King William Street was the original terminus of the first deep level electric Tube in the world and now this station is part of the Bank upgrade project. Siddy shows Tim its Second World War shelters, original Victorian tiles and steep running tunnels and where it goes under the Thames.

Siddy also visits Knightsbridge, where old lift shafts taken out of service in the 1930s are now being put back into use to make the station accessible for all.

Tim and Siddy explore the disused parts of London Bridge. Siddy visits Ongar in Essex, and nearby Blake Hall which, at the end, served less than 20 passengers a day.