The tunnels are eeires and somehow unsettling, like pictures of the deep ocean floor or the craters upon Mars.
Peter Akroyd, London Under

Yesterday I finished the (refreshingly) concise London Under by Peter Ackroyd. It’s one of those books where at every page turn you make a mental note to Google a particular story. Inevitably I usually forget.

On this occasion one such story I did remember is journalist’s Duncan Campbell’s bike ride into the sprawling network of hidden Government tunnels - 100 feet below central London.

In 1980, the investigative journalist Duncan Campbell entered this network via a manhole on a traffic island in Bishopsgate. He rode a collapsible bike around it, apparently while guards were having their tea, photographed it, and described it in an article published in the Christmas 1980 edition of this magazine. 
Tunnel vision, Andrew Martin

I found the photographs tricky to track down but thanks to Wikipedia and The Wayback Machine I uncovered these photos by Chris Davies with notes by Duncan Campbell. 

Photographs © Chris Davies