They are a hidden maze of tunnels where a bloody underground war was played out in terrifying darkness and where the bodies of 28 heroes lie entombed forever.

Now, after lying practically undisturbed since troops laid down their arms in 1918 and just days before Remembrance Sunday, the secrets and tragedies of the labyrinth are finally being revealed thanks to work by archaeologists.

Since January, the Anglo-French La Boiselle Study Group has been working with historians to open up and explore the tunnels to discover more about the lives of the men lost in them....