And here's the reason I just went for a fairly pointless wander around the station—I thought I'd kill a little time so I could snap a train actually using the Clifton Extension Railway's tunnel as my last picture of the wander.
A quick google of the number suggests this is a Great Western Railway Class 166, whatever that means. I quite like trains, but I'm no trainspotter.
That concludes our rather random 9km wander around the above-ground bits of a tunnel. Please disembark safely, minding the gap between this website and the rest of the internet.
GPS Coordinates:
51.46434, -2.61340
Location: Whatley Road