Professor Horatio Pendulum has a confession to make. The Chronosphere — his magnificent machine, hidden beneath the Timeporium Clock Shop — was only ever meant to peer safely into history. Instead he's overloaded it, torn a rift in time and scattered fragments of the past across the City of London. Roman soldiers are marching through the streets. There's a smell of burning bread in the air. And history, as the Professor puts it, is leaking.

That's where you come in. Join Dan and Bex as they follow the Chronosphere's riddles from landmark to landmark, meeting the lost travellers stranded in the wrong century — and helping every single one of them find the way home.

Before you set off: download the Time Hunter handbook for the map, the facts and space to write down everything you find. And pick yourself a suitably ancient alias while you're at it — Caesar Saladus if you're feeling peckish, Octavius Oops if you're a bit clumsy.