actually, that picture doesn't show the station roof, he was never at or near the station. that's the HS1 "portal" where the tracks dip into the tunnel to Stratford at the point where the line crosses the Thameslink connections to/from the ECML - see the concrete retaining walls on the left. immediately under the portal cover, and accessible from the far end (in front of the flag waver) is the 25kV electric traction equipment - all of which is live except the steel supporting structures.