I first went down here in July with ratfink and oliver gt, discovering it was a awesome extra to the small section of the tunnels above and at the time i had no camera. I decide to return with my pal heXt for some tee light experiments.
"the rat hole" runs from just south of Primrose Hill Tunnel where it used to connect to the up slow Broad Street line which in turn connected to the up slow Euston line just prior to the Central Tunnel Mouth. The North London line diverged from the Euston line at this point line and crossed over the Euston electric lines which are in tunnel at this point and the Rat hole diverges to the east before swinging west it then heads under the North London line just before Chalk Farm Station and emerged having crossed under the west coast main line on the Euston access route to Camden Locomotive Shed - now off peak sidings for Silverlink