The clockwork conspiracy by Sam Sedgman

Aspiring inventor Isaac Turner lives with his dad, the Chief Horologist in charge of Big Ben. But when his father vanishes from the belfry on the night the clocks go back, leaving behind only a smashed pocket watch and a cryptic message, Isaac determines to find him. Hunting a trail of clues through London’s landmarks, Isaac uncovers a sinister plot in the gears of government and embarks on a race against time to save his father – and time itself.