Two lost Underground stations, connected by tunnels now empty of passengers: Euston is full of secrets. When the old station and its famous Doric arch were replaced with the current building, access to the Tube was also updated and on 29 April 1962, the old passages were closed to the public. With no reason to change the advertising, these posters - many torn and ragged - were left behind as a sort of time capsule.
The passage was originally built to link the City & South London Railway's station (on what is now the Bank branch of the Northern Line) to the Charing Cross, Euston & Hampstead Railway's (now the Northern Line's Charing Cross branch). The C&SLR had opened their building on Eversholt Street in May 1907; it was lost in the 1960s demolitions. The CCE&HR's Leslie Green building can still be seen on the corner of Drummond Street and Melton Street, although it now houses ventilation equipment for the Victoria Line.
A few remnants of the original decor remain. This tiled frieze has been painted over, but the distinctive green color shows through here and there.
The tunnel joining the two stations below ground could be entered from the mainline station by lift. The lift shaft is now empty.
However, traces of the ticket office still remain.
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I visited the passages on one of the London Transport Museum's Hidden London events. All current tours of Euston are sold out, but there are still a few places on visits to Clapham South and Down Street. Maybe one day, they will offer visits to another advertising time capsule? 
