Inside the Blackheath railway tunnel: Battling water damage and the weather

When you’re working half a mile inside a railway tunnel under south London, how windy it is on the surface shouldn’t affect you – but as they’ve found in Blackheath, it can.
Blackheath Tunnel (c) Network Rail
The Blackheath railway tunnel, which this year marks its 175th anniversary, is currently closed for repairs due to damage from water ingress, and it has proven to be a challenging site to work in.
But first, why is there a tunnel here at all?
If you look at a modern