Guy helps to overhaul a steam locomotive used on the popular Severn Valley Railway, a 16-mile stretch of track in Shropshire preserved to look just as it did in the 19th century.
He joins a team of volunteers, some as young as 17, to help repair its boiler, safety valves and one of its two-tonne wheels.
He also lays some track using exactly the same methods as the notorious 'navvies' - the hard-drinking, hard-living labourers who laid Britain's railway infrastructure by hand.
Guy learns the dying arts of the Victorian blacksmith to make a coal shovel out of wrought iron, and repairs a century-old train driver's pocket watch using washers just 1mm wide.
If everything can be made to work then Guy will get the chance to try his hand at every young boy's dream job: steam train driver.
