I noticed that this agency did not yet have a thread, so this is it. They are a first class agency, one of the oldest in London, highly recommended. Sarah was my agent from 1998 - 2004. She is wonderful, but has since switched to children's lit only. All of her clients have moved to other agents within the agency as a result. They are very personal and take great care of their clients, as you can see from this thread.
When I was with them they had this wonderful quirky office in St Martin's Lane, lots of up-and-down slanting staircases over several floors. Then they moved to what I suppose are really nice modern offices; I never got to see the new place.