Rob explores the construction of the world's first deep Tube Line known today as the Northern Line, which runs 36 miles through London and connects the boroughs north and south of the Thames. 700,000 passengers rely on it every day.

The Central Line is the artery that travels across the heart of London. At 46 miles, it is the longest of all tube lines. But as Rob discovers, it is a line constantly battling it's Victorian legacy.

London's Metropolitan Line was the world's first underground railway, and is still used by 70 million passengers each year.

The Piccadilly Line is famed for its glamorous stops, but Rob Bell discovers how it also changed public transport as we know it.