Theater Tickets, London

The TKTS booth in Leicester Square, or sometimes the box office for returns. Make SURE you are at the standalone booth, and not the pretend-to-be-TKTS agencies on the way there.

http://www.tkts.co.uk/

However, just like Times Square in NYC, the TKTS booth can have quite a line. I've had reasonable luck dealing with the other ticket brokers in the area (I recall using one inside of the Licester Square tube station). While more expensive than the TKTS office, I was still able to get good prices for same-day tickets.

Thank you for your help. Now I am ready for theater in London.

You might also want to spend some time on these sites: http://londontheatre.co.uk/
http://theatremonkey.com/

You might also try stopping by the box office of the theatre itself in the morning. I don't know if it is cheaper or not, but it is worth a try.

there are also Ticket agents if there is a show you decide you really want to see. I would try the Tickets booth first before going to the actual box office. There are usually some really good shows available (and you do save money)

I agree with Steve-go to the ticket booth of the theater of the play you want to see. Recently we have seen Wicked and Oliver! and got great tickets for around 28 BP per ticket. The Leicster Square booth is good if you don't have a particular play in mind.

Lastminute.co.uk also has some great deals if you'll have Internet access while you're there. In most if not all cases, it's a gamble because you can't pick your exact seat, but in the two or three times I purchased tickets from them, I wasn't disappointed.