They aren't the big grand theatres, they are smaller venues that are full of atmosphere or have the coolest bars to hang out in. This is my top five:

1. Royal Court

The cafe bar serves the best chips in London (according to @polyg), take your time walking down the stairs to scan the crowd because you are virtually guaranteed to spot a thesp/director/writer. Get there early and you'll often find one or two of the Royal Court cast members lounging around on one of the sofas or having a quick drink with friends.

2. Old Vic Tunnels

Now that the Southwark Playhouse has temporarily moved from its under-the-railway-arches home at London Bridge, the Old Vic Tunnels is the place to go for your fix of theatre with a damp smell, low-lighting and trains rumbling overhead. You approach it from a down at heel street around the back of Waterloo. Blink and you miss the nondescript door but inside it oozes atmosphere, character and quirky features and feels like you've found a secret club.

3. Arcola Theatre

If you thought being able to take a real glass of something into the auditorium was cool and grown up, try settling down to watch a play with a... mug of tea. Yes, the Arcola will let you take a cuppa in with you, that's if you can get off the lovely saggy, leather sofa in the cafe bar.