In pictures: see inside London's secret Mail Rail tunnels

Have you heard about the new tube line? Well, it's sort of new. The Post Office Underground Railway is set to re-open as a museum and underground ride. The Mail Rail originally opened in 1927, shuttling post around London for almost 80 years before its closure in 2003.

Stretching from Whitechapel in the East End to Paddington in the west, the line was considered so clandestine that it was used to stash the Rosetta Stone during the First World War. 

The disused tunnels will be revamped into the British Postal Museum & Archive’s new Postal Museum. From mid-2017, transport geeks, postal buffs and the rest of us will be able to hitch a ride on the refurbished Mail Rail, when it opens to the public for the first time.

Get a sneak peek inside the Mail Rail tunnels with these pics: 

And check out this behind-the-scenes video from the Mail Rail tunnels:

Enjoy hanging out underground? Take a look at these 17 awesome photos of tunnels in London.