Tiles of the Unexpected Underground

Ah yes Euston is very very interesting and I had occasion to expore it more than once. I have walked all the vent passageways and surveyed all the cable routes including the ladder up from the disused passageway to the old lift area that enters the floor of one of the escalator chambers above. What I recall about that is that the chamber is unusually cramped and one cannot walk around in it as the ceiling is perhaps no more than 4' from the floor. The chamber is normally entered through a hatch from the mid level circulating passageway area.
When I last worked there much of the disused passeway area was being converted into UPS switchrooms so the passageway was being divided into lots of rooms much as was done in the disused subterranean area at Liverpool Street during the Broadgate development. It was a shame as the walls still had the old advert posters and closure notices dating back to 1961 IIRC. I can recall Euston mainline being rebuilt around that time though I was just a nipper back then, the family using Euston en route to Holyhead.
One of the great joys of having to run cable all over the combine was visiting, exploring and surveying the disused areas to be found at almost all the tube stations.