The first book in the Maudlin Towers series.
"Beware this fiendish new illustrated adventure! It has been flying off and around the shelves like a mischievous bat.
Pin it down, open it up and you will discover peculiar goings on at Maudlin Towers School for the Not Particularly Bright Sons of the Not Especially Wealthy. There's a viking in the sports grounds, a ghost in the attic, a werewolf on the stairs and — at the heart of it all — a temporo-trans-navigational-vehicular engine (armchair modified into a time machine). One can only hope best chums Mildew and Sponge will do their utmost to restore order, while at the same time avoiding being eaten by a werewolf, chopped up by vikings or horribly punished by their eccentric cast of teachers. Best of luck, chaps."