American Express -- The main Amex office is at 30-31 Haymarket, SW1 (tel. 020/7484-9600; Tube: Piccadilly Circus). Full services are available Monday through Saturday from 9am to 6pm. On Sundays from 10am to 5pm, only the foreign-exchange bureau is open.

Babysitters -- Babysitting organizations provide registered nurses and carefully screened mothers, as well as trained nannies, as sitters. One such company is Childminders (tel. 020/7935-2049; www.babysitter.co.uk; Tube: Baker Street). You pay £7 ($11) per hour in the daytime and £6 to £8 ($9.60-$13) per hour at night. There's a 4-hour minimum, and hotel guests pay a £11.50 ($18) booking fee each time they use a sitter. You must also pay reasonable transportation costs.

Business Hours -- Banks are usually open Monday through Friday from 9:30am to 3:30pm. Business offices are open Monday through Friday from 9am to 5pm; the lunch break lasts an hour, but most places stay open during that time. Pubs and bars stay open from 11am to 11pm Monday through Saturday and from noon to 10:30pm on Sunday. Stores generally open at 9am and close at 5:30pm, staying open until 7pm on Wednesday or Thursday. Most central shops close on Saturday around 1pm. In a recent change, some stores are now open for 6 hours on Sunday, usually from 11am to 5pm.

Camera Repair -- Sendean, Shop 2, 9-12 St. Anne's Court, W1V (tel. 020/7439-8418), gives free estimates and does quick work. It's open weekdays from 10am to 5pm (Fri until 6pm) and accepts MasterCard and Visa.

Dentists -- For dental emergencies, call Eastman Dental Hospital (tel. 020/7915-1000; Tube: King's Cross or Chancery Lane).

Doctors -- Call tel. 999 in a medical emergency. Some hotels have physicians on call for emergencies. For non-emergencies, try Medical Express, 117A Harley St., W1 (tel. 020/7499-1991; Tube: Regent's Park). A private British clinic, it's not part of the free British medical establishment. For filling the British equivalent of a U.S. prescription, there's sometimes a surcharge of £20 ($32) on top of the cost of the medications. The clinic is open Monday through Friday from 9am to 5:30pm and Saturday from 9:30am to 2pm.

Drugstores -- In Britain they're called chemists. Every police station has a list of emergency chemists (dial 0 and ask the operator for the local police). One of the most centrally located, keeping long hours, is Bliss the Chemist, 5 Marble Arch, W1 (tel. 020/7723-6116; Tube: Marble Arch), open daily from 9am to midnight. Every London neighborhood has a branch of Boots the Chemist, Britain's leading pharmacy, which is also open until midnight.

Electricity -- British current is 240 volts, AC, so you'll need a converter or transformer for U.S.-made electrical appliances, as well as an adapter that allows the plug to match British outlets. Some (but not all) hotels supply them for guests. If you've forgotten one, you can buy a transformer/adapter at most branches of Boots the Chemist.

Embassies & High Commissions -- If you lose your passport or experience some other emergency, here's a list of addresses and phone numbers: Australia The high commission is at Australia House, Strand, WC2 (tel. 020/7379-4334; Tube: Charing Cross or Aldwych); it's open Monday through Friday from 9am to 5:30pm. Canada The high commission is located at MacDonald House, 38 Grosvenor Sq., W1 (tel. 020/7258-6600; Tube: Bond Street); it's open Monday through Friday from 8am to 4pm. Ireland The embassy is at 17 Grosvenor Place, SW1 (tel. 020/7235-2171; Tube: Hyde Park Corner); it's open Monday through Friday from 9am to 1pm and 2 to 5pm. New Zealand The high commission is at New Zealand House, 80 Haymarket at Pall Mall, SW1 (tel. 020/7930-8422; Tube: Charing Cross or Piccadilly Circus); it's open Monday through Friday from 9am to 5pm, but hours vary by department. The United States The embassy is at 24 Grosvenor Sq., W1 (tel. 020/7499-9000; Tube: Bond Street). For passport and visa information, go to the U.S. Passport & Citizenship Unit, 55-56 Upper Brook St., W1 (tel. 020/7499-9000, ext. 2563 or 2564; Tube: Marble Arch or Bond Street). Embassy hours are Monday through Friday from 8:30am to 5:30pm. Passport & Citizenship unit hours are Monday through Friday from 8:30 to 11:30am and Monday, Wednesday, and Friday from 2 to 4pm.

Emergencies -- For police, fire, or an ambulance, dial tel. 999.

Eyeglass Repair -- David Clulow has 10 offices in Central London; the one in Soho, 70 Old Compton St., W1 (tel. 020/7287-1128), can handle most repairs and fills eyeglass prescriptions.

Hospitals -- The following offer emergency care in London 24 hours a day, with the first treatment free under the National Health Service: Royal Free Hospital, Pond Street, NW3 (tel. 020/7794-0500; Tube: Belsize Park); and University College Hospital, Grafton Way, WC1 (tel. 020/7387-9300; Tube: Warren Street or Euston Square). Many other London hospitals also have accident and emergency departments.

Hot Lines -- For police or medical emergencies, dial tel. 999 (no coins required). If you're in some sort of legal emergency, call Release at tel. 020/7729-9904, 24 hours a day. The Rape Crisis Line is tel. 020/7837-1600 or 020/8572-0100, accepting calls after 6pm. Samaritans, 46 Marshall St., W1 (tel. 020/7734-2800; Tube: Oxford Circus or Piccadilly Circus), maintains a crisis hot line that helps with all kinds of trouble, even threatened suicides. Doors are open from 9am to 9pm daily, and phones are open 24 hours. Alcoholics Anonymous (tel. 020/7833-0022) answers its hot line daily from 10am to 10pm. The AIDS 24-hour hot line is tel. 0800/567-123.

Legal Aid -- In every case where legal aid is required by a foreign national within Britain, the British Tourist Authority advises visitors to contact their Embassy.

Liquor Laws -- No alcohol is served to anyone under 18. Children under 16 aren't allowed in pubs, except in certain rooms, and then only when accompanied by a parent or guardian. Pubs are open Monday through Saturday from 11am to 11pm and Sunday from noon to 10:30pm. Restaurants are allowed to serve liquor during the same hours as pubs; however, only people eating a meal on the premises can be served. You can buy beer, wine, and liquor in supermarkets, liquor stores (called off-licenses), and many local grocery stores during any hour that pubs are open. In hotels, liquor may be served from 11am to 11pm to both residents and nonresidents; after 11pm, only residents may be served. Any nightclub that charges admission is allowed to serve alcohol until 3am or so. Don't drink and drive; penalties are stiff.

Lost & Found -- Be sure to tell all of your credit-card companies the minute you discover your wallet has been lost or stolen, and file a report at the nearest police precinct. Your credit-card company or insurer may require a police report number or record of the loss. Most credit-card companies have an emergency toll-free number to call if your card is lost or stolen; they may be able to wire you a cash advance immediately or deliver an emergency credit card in a day or two. Visa's U.S. emergency number is tel. 800/847-2911 or 410/581-9994. American Express cardholders and traveler's check holders should call tel. 800/221-7282. MasterCard holders should call tel. 800/307-7309 or 636/722-7111. For other credit cards, call the toll-free number directory at tel. 800/555-1212.

In Britain, for Amex issues call tel. 0208/551-1111; for Visa and MasterCard issues, call tel. 0870/242-4240.

If you need emergency cash over the weekend when all banks and American Express offices are closed, you can have money wired to you via Western Union (tel. 800/325-6000; www.westernunion.com).

Identity theft or fraud are potential complications of losing your wallet, especially if you've lost your driver's license along with your cash and credit cards. Notify the major credit-reporting bureaus immediately; placing a fraud alert on your records may protect you against liability for criminal activity. The three major U.S. credit-reporting agencies are Equifax (tel. 800/766-0008; www.equifax.com), Experian (tel. 888/397-3742; www.experian.com), and TransUnion (tel. 800/680-7289; www.transunion.com). Finally, if you've lost all forms of photo ID, call your airline and explain the situation; they might allow you to board the plane if you have a copy of your passport or birth certificate and a copy of the police report you've filed.

Mail -- An airmail letter to North America costs 45p (70¢) for 10 grams; postcards require a 40p (65¢) stamp; letters generally take 7 to 10 days to arrive from the United States. See "Post Offices," below, for locations.

Newspapers & Magazines -- The Times, Daily Telegraph, Daily Mail, and Guardian are dailies carrying the latest news. The International Herald Tribune, published in Paris, and an international edition of USA Today, beamed via satellite, are available daily (USA Today will be printed as a newsletter). Copies of Time and Newsweek are sold at most newsstands. Magazines such as Time Out, City Limits, and Where contain useful information about the latest happenings in London.

Passports -- For Residents of the United States: Whether you're applying in person or by mail, you can download passport applications from the U.S. State Department website at http://travel.state.gov. For general information, call the National Passport Agency (tel. 202/647-0518). To find your regional passport office, either check the U.S. State Department website or call the National Passport Information Center (tel. 900/225-5674); the fee is 55¢ per minute for automated information and $1.50 per minute for operator-assisted calls.

For Residents of Canada: Passport applications are available at travel agencies throughout Canada or from the central Passport Office, Department of Foreign Affairs and International Trade, Ottawa, ON K1A 0G3 (tel. 800/567-6868; www.dfait-maeci.gc.ca/passport).

For Residents of Ireland: You can apply for a 10-year passport at the Passport Office, Setanta Centre, Molesworth Street, Dublin 2 (tel. 01/671-1633; www.irlgov.ie/iveagh). Those under age 18 and over 65 must apply for a €12 3-year passport. You can also apply at 1A South Mall, Cork (tel. 021/272-525) or at most main post offices.

For Residents of Australia: You can pick up an application from your local post office or any branch of Passports Australia, but you must schedule an interview at the passport office to present your application materials. Call the Australian Passport Information Service at tel. 131-232, or visit the government website at www.passports.gov.au.

For Residents of New Zealand: You can pick up a passport application at any New Zealand Passports Office or download it from their website. Contact the Passports Office at tel. 0800/225-050 in New Zealand or 04/474-8100, or log on to www.passports.govt.nz.

Police -- In an emergency, dial tel. 999 (no coins required). You can also go to a local police station in central London, including New Scotland Yard, Broadway, SW1 (tel. 020/7230-1212; Tube: St. James's Park).

Post Offices -- The main post office is at 24-28 William IV St. (tel. 020/7484-9307; Tube: Charing Cross). It operates as three separate businesses: inland and international postal service and banking (Mon-Fri 8:30am-6:30pm and Sat 9am-5:30pm); philatelic postage-stamp sales (Mon-Sat 8am-8pm) for collectors; and the post shop, selling greeting cards and stationery (Mon-Sat 8:30am-6:30pm). Other post offices and post-office branches are open Monday through Friday from 9am to 5:30pm and Saturday from 9am to 12:30pm. Many post-office branches and some main post offices close for an hour at lunchtime.

Radio -- There are 24-hour radio channels operating throughout the United Kingdom, including London. They offer mostly pop music and chat shows at night. Some "pirate" stations add more spice. So-called legal FM stations are BBC1 (104.8); BBC2 (89.1); BBC3 (between 90 and 92); and the classical station, BBC4 (95). There is also the BBC Greater London Radio (94.9) station, with lots of rock, plus LBC Crown (97.3), with news and reports of "what's on" in London. Pop/rock U.S. style is heard on Capital FM (95.8); if you like jazz, reggae, or salsa, tune in to Choice FM (96.9). Jazz FM (102.2) offers jazz, blues, and big-band music.

Restrooms -- They're marked by PUBLIC TOILETS signs in streets, parks, and Tube stations; many are automatically sterilized after each use. The English often call toilets "loos." You'll also find well-maintained lavatories in all larger public buildings, such as museums and art galleries, large department stores, and railway stations. It's not really acceptable to use the lavatories in hotels, restaurants, and pubs if you're not a customer, but we can't say that we always stick to this rule. Public lavatories are usually free, but you may need a small coin to get in or to use a proper washroom.

Smoking -- Most U.S. cigarette brands are available in London. Smoking is forbidden in the Underground (on the cars and the platforms) and on buses, and it's increasingly frowned upon in many other places. But London still isn't a particularly friendly place for the nonsmoker. Most restaurants have nonsmoking tables, but they're usually separated from the smoking section by only a little bit of space. Nonsmoking rooms are available in the bigger hotels. Some of the smaller hotels claim to have nonsmoking rooms, but we've often found that this means the room is smoke-free only during our visit; if you're bothered by the odor, ask to be shown another room.

Taxes -- There is a 17.5% national value-added tax (VAT) added to all hotel and restaurant bills and included in the price of many items you purchase. It can be refunded if you shop at stores that participate in Global Refund Tax-Free Shopping (signs are posted in the window).

You also pay a departure tax of £10 ($16) for flights within Britain and the European Union; it's £20 ($32) for flights to the U.S. and other countries. Your airline ticket may or may not include this tax. Ask in advance to avoid a surprise at the gate.

To encourage energy conservation, the British government levies a 25% tax on gasoline (petrol). If you've read our warnings about driving in London, this will be of no importance to you whatsoever.

Telephone -- To call London: If you're calling London from the United States:

1. Dial the international access code: 011.

2. Dial the country code 44.

3. Dial the city code 20 and then the number. (London's official city code is 020, but you will dial 20 because you always have to omit the zero from the area code when calling London from outside of England.) So the whole number you'd dial would be 011-44-20-0000-0000.

To make international calls: To make international calls from London, first dial 00 and then the country code (U.S. or Canada, 1; U.K., 44; Ireland, 353; Australia, 61; New Zealand, 64). Next you dial the area code and number. For example, if you wanted to call the British Embassy in Washington, D.C., you would dial 00-1-202-588-7800.

Or call through one of the following long-distance access codes: AT&T USA Direct (tel. 0800/890-011), Canada Direct (tel. 0800/890-016), Australia (tel. 0800/890-061), or New Zealand (tel. 0800/890-064). Common country codes are U.S. and Canada, 1; Australia, 61; New Zealand, 64; South Africa, 27.

For directory assistance: Dial tel. 142 if you're looking for a number inside London, dial tel. 192 if you're looking for a number in the rest of Britain, and dial tel. 100 for numbers in all other countries.

For operator assistance: If you need operator assistance in making a call, dial tel. 100 if you're trying to make an international call and tel. 192 if you want to call a number in England.

Toll-free numbers: Numbers beginning with 0800 within London are toll-free, but calling a 1-800 number in the States from England is not toll-free. In fact, it costs the same as an overseas call.

To call within London: Dial the local seven- or eight-digit number.

To call within Britain (outside of London): Phone numbers outside the major cities consist of an exchange code plus telephone number. To dial the number, you need to dial the exchange code first. Information sheets on call-box walls give the codes in most instances. If your code isn't there, call the operator by dialing tel. 100.

There are three types of public pay phones: those taking only coins, those accepting only phonecards (called Cardphones), and those taking both phonecards and credit cards. At coin-operated phones, insert your coins before dialing. The minimum charge is 10p (15¢).

Phone cards are available in four values -- £2 ($3.20), £5 ($8), £10 ($16), and £20 ($32) -- and are reusable until the total value has expired. Cards can be purchased from newsstands and post offices. You can also use credit cards -- Access (MasterCard), Visa, American Express, and Diners Club -- at credit-call pay phones, commonly found at airports and large railway stations.

Time Zone -- England follows Greenwich Mean Time (5 hr. ahead of Eastern Standard Time). Most of the year, Britain is 5 hours ahead of the time observed on the East Coast of the United States. When it's noon in New York, it's 5pm in London. Because the U.S. and Britain observe Daylight Savings Time at slightly different times of year, there's a brief period (about a week) in the spring when London is 6 hours ahead of New York.

Tipping -- In restaurants, service charges in the 15% to 20% range are usually added to the bill. Sometimes this is clearly marked; at other times, it isn't. When in doubt, ask. If service isn't included, it's customary to add 15% to the bill. Sommeliers get about £1.95 ($3.10) per bottle of wine served. You can leave small change if the service is good. There's no tipping in pubs. In cocktail bars, the server usually gets about 75p ($1.20) per round of drinks.

Hotels, like restaurants, often add a service charge of 10% to 15% to most bills. In smaller B&Bs, the tip isn't likely to be included. Therefore, tip people who performed special services, such as for the person who served you breakfast. If several persons have served you in a B&B, many guests ask that 10% or 15% be added to the bill and divided among the staff. Tip chambermaids $1 per day for cleaning up (more if you've made their job extra difficult).

It's standard to tip taxi drivers 10% to 15% of the fare, although a tip for a taxi driver should never be less than 30p (50¢), even for a short run. Barbers and hairdressers expect 10% to 15%. Tour guides expect £3 ($4.80), although it's not mandatory. Theater ushers don't expect tips.

Transit Information -- For more information on travel on London's Tube and bus system, call tel. 020/7222-1234, 24 hours a day.

Water -- London's water is safe to drink. Tap water is free in restaurants, so be sure to ask for it if you don't want to pay for bottled water.

Weather -- Call tel. 020/7922-8844 for current weather information, but chances are the line will be busy. You can also tune into 1152 AM (The Voice of London) for weather reports.