My adult (mid 20s) son and I are meeting ... cancel question ...
the british museum and westminster cathedral were two of the most wonderful parts of my entire england trip. and for shopping, do NOT skip the amazing camden market!
i'm jealous.
:) khairete
S.
Manda F has said it well! The only things I'd add if you have time; take a boat trip up the Thames and, suitably prepared for incessant rain, take an open-topped double decker guided bus tour.
My husband is English so we are over there every year and I went to school there. Great city.
Markets -- forget shopping malls. Boring chain stores there just like here. He will love the markets instead just as you will. Camden market as someone noted but there are MANY other local markets -- some are food markets (like farmer's markets) but you want the ones in areas like Camden or Notting Hill. Ask your hotel concierge which ones would have secondhand stalls. Look online and search before you go. Oxford Street is crowded and noisy and there are pickpockets, chain stores and dumpy tourist shops -- it's OK to walk through once but not a destination I would choose for fun shopping.
History is overwhelming so he should do some homework in advance about where he wants to go. The British Museum is amazing as others note but look at its site and see if there are exhibits you want -- there is a lot of ancient history there (Egyptian, Greek, etc.). For history that's more on-site and British, go to the Tower of London (lines can be long, check about best times to go when it's not too crowded); Hampton Court Palace (at least half a day if not a whole day -- just outside central London but THE place to go if he's interested in Tudor history) -- really spend time researching, because London offers so much and is so sprawling it's good to go with ideas in mind for each day, so you don't end up making a last-second choice that ends up taking you ages to get to on the Tube, for instance.
Be warned that prices will seem very steep. The exchange rate with the pound has been in their favor, not ours, for years. You can eat more cheaply (and quickly, leaving more time for tourism) by popping in to grocery stores, picking up sandwiches, yogurts, etc. and eating them in the nearest park (of which there are many). We do that for lunches and then spend more for a sit-down meal at dinner.
Go to the theatre. Please. You can book tickets from here or the Middle East before you go.
As for areas, hard to be objective. "Best area" could mean cleanest, or it could mean most convenient for tourism, or it could mean cheapest -- you won't get all three in the same place! We stay in central London because it really adds travel time if you stay too far out. We like a chain called Ibis hotels; there is one near Euston rail station, I think. There are also heaps of "hotels" that are more like B&Bs in the area around Paddington rail station, which is very central. Be aware that these "hotels" and things they call "B&Bs" are often not fancy like here -- they tend to be very, very basic and the breakfasts very basic or even not great. But they are centrally located near Tube and rail stations. To know what you're getting you can go with a chain like Ibis or even the chains such as Best Western, Hilton, etc. but they will cost much more.
Oh, soooo jealous! London is my favorite city. Definitely do your research before you go--the are literally thousands of things to do/see. It's hard to pick! I like Rick Steves' Guide Books.
I've always had good luck with hotels.com. Stay as central as possible (inside Zone 1 on the London Tube Map). I did a semester and lived by Tottenham Court Rd/British Museum.
Definitely see a show!!!
HAVE FUN!!!!
