Creaky Castle: Tom and the Siege by Tony Bradman
Usborne Publishing ISBN 9780746081211
Tom has finally pushed his luck too far! His mother, Lady Eleanor, is determined to send him to the terrifyingly tough Squire School, for a life of long-distance runs and cold baths, to make him behave. Only a full-scale siege of Creaky Castle could possibly stop Lady Eleanor's plans. Luckily, the villainous Bad Bart is happy to oblige.... Devilish deals, battering rams and exploding cows.... it's a medieval battleground at Creaky Castle!