[London] Pre or post theatre restaurant?
in terms of post theatre there are plenty of good restaurants, but i'd suggest the places that specialise in later service and actually have an influx of people so you have some form of atmosphere. nothing worse than being sat in a restaurant, however good, only to be rushed out the door with few, if any tables, around you.
with this in mind the most obvious suggestion would be the ivy, which isn't as difficult to get into these days, especially if you have a bit of time between now and the date of the show. i'd also recommend the wolsey, le caprice, j.sheeky, quo vadis, the new hix and bob bob ricard, all of which have ok food and a later scene (though do check).
if you fancy chinese there's obviously a load right on your door step, not least the excellent bar schu.
finally, if you want top end food, consider l'atelier joel robuchon which i personally think deserved its 2 star elevation last year. the only caveat being you'll pay accordingly!