You are indeed correct
it's biscuits - I seem to remembers Douglas saying in a interview that this happened to him
(
fastcar,
Mon 5 Oct 2009, 12:32,
archived)
But, but, but
Bill Bryson said it happened to him in "Notes from a Small Island"!
(
Quijibo Esq. BSc. May contain traces of nuts,
Mon 5 Oct 2009, 13:14,
archived)