Picked this Ronald Searle 1953 classic a couple of weeks ago from a bookshop in Edinburgh (Till's brilliant second-hand bookshop is full of treasures like this, comics, old film posters and much more... here's their website http://www.tillsbookshop.co.uk/index.aspx if anybody wants to check them out).
The main character, Nigel Molesworth, had already been created by Geoffrey Willans for Punch magazine before Searle was approached to produce the characters for the story. Following its huge success (which, incidentally, surpassed the sales of "The Terror Of St. Trinian's"(1952) that Searle is more famous for) there were two more books published in the same series before the author's death in 1958. More details on wikipedia here: http://en.wikipedia.org/wiki/Nigel_Molesworth