I just saw it: Kristen Scott Thomas, Douglas Hensall and Ben Miles with John Guerrasio as the waiter.
If you can see it, do it. It was the best Betrayal I have seen and particularly good acting from Kristen and Douglas. The production manages to bring out the humour, which then makes the pathos sader.
I think Kristen is currently the best actress on the London stage (I previousley saw her in Pirandello and in Chekhov).