London's disused Tube stations and hidden tunnels set to open to the public

Grab your hard hat. Fetch a torch. London is about to expose its darkest secrets.

Not figuratively - literally. Hidden London is tripling the number of tickets available for tours of seldom seen locations on the Underground system, taking in close stations, unused shelters and abandoned tunnels.

Organised by London Transport Museum (LTM), subterranean locations set to be opened to the public include:

• The 'lost' tunnels of Euston station, featuring vintage poster artwork from decades past and a hidden space beneath the current station
• Down Street - a small, secretive station located between Hyde Park Corner and Green Park, closed to the public in 1932 and later used in World War II
• The subterranean deep-level shelters under Clapham South, used in the heights of the Blitz and later to house Caribbean migrants
• A behind-closed-doors tour of the disused sections of Charing Cross station, including the tunnels that run under Trafalgar Square

A secretive above-ground location set to be open for tours is 55 Broadway - London's first skyscraper and former headquarters of the Underground. 

Around 17,000 tickets for Hidden London will go on sale at 23:59 on 18 April, with some tours offering more ticket places than others (it's a bit of a squeeze into Down Street). To stand a chance of bagging a ticket, you'll need to sign up to the LTM newsletter.

You can find out more about the tours here. We'll see you in the shadows.