Custardfinger by Philip Reeve
Praise for this series: "A winner . an enjoyable laugh-out-loud romp" Guardian The fourth book in the Buster Bayliss series, Custardfinger is a hilarious James Bond spoof. Buster is reluctantly forced to save the world yet again, this time from Myrtle Burtle, his school dinner lady. Myrtle has plans for world domination by means of custard, and she's armed and dangerous.