It was built as a normal railway in 1867 hence the other older platforms near the bat tunnel. Then rebuilt in the 1880's, also added to in 1935 for the underground line as you see it now.
Would of originally gone via Alexandra palace to finsbury park connecting up to the northern line via drayton park , and to east finchley as part of the proposed Northern heights extension of the northern line after the war . 1954 was the last time goods trains ran through those tunnels , 1970 was when the track through the station and the tunnels were lifted .mainline size bores for the tunnel design but yet intended for tube stock as proposed , locals have heard the sound of a train in that location , not beneath, but actually above ground through that station .On your return back , the live railway you see leads up to high gate depot sidings , which is a stabling point for the northern line
The corrugated section 01:11 between the platforms is in fact the roof of the underground part of the station below. You lucky sods! I've always wanted to see inside the tunnels 07:00 and not for the bloody bats neither. The oval shape is because they were built for main line stock which was steam powered of course and the extra height is for the steam to have somewhere to dissipate. The little nooks 09:04 are for line workers to duck into when a train was coming.
ALSO THE MORE STANDARD TUBE TUNNEL LOOKING NORTH INTO WARDS HIGHGATE DEPOT WAS A REPAIR JOB AFTER WWII AIR RAID HIGHGATE DEPOT WAS ALSO THE HOME OF THE ROYAL TRAIN WHICH HAD IT OWN SHED COVERING BOTH ENGINERS SIDING AND 1 ROAD AS THEY ARE KNOWN TODAY
That is so odd, one tunnel has a fence at the end, and the other has a brick wall. Why the heck wouldn't they be similar since the both have doors at the other end.