1/10Tim Dunn explores disused tube station Down Street, which played a crucial role in WWII.(R)
2/10Tim Dunn visits the Ffestiniog in Wales, originally built to transport slate to the coast.(R)
3/10Tim Dunn goes behind the scenes at London's Kings Cross station.(R)
4/10Tim Dunn visits the Ribblehead Viaduct in the Yorkshire Dales.(R)