As Lancaster and Powell were good friends, it is likely that the exhibition will be of interest to AP aficionados, although I don't know if there will be any AP material.
Cartoons and Coronets: The Genius of Osbert Lancaster
Thursday 2nd October 2008 - Sunday 11th January 2009
Osbert Lancaster was one of the most famous artistic personalities of his day, renowned as an architectural satirist, illustrator, theatre designer and cartoonist. This exhibition, which marks the centenary of his birth, will celebrate the astonishing range of Lancaster as an artist and as a chronicler of style and fashion, drawing on an unparalleled archive of original designs, illustrations, works on paper, sketchbooks, theatre sets and photographs, none of which have ever been previously exhibited.
For further information keep an eye on the Wallace's exhibition page.