Possible creature sighting on London Underground, November - what was that?

I'm posting this anonymously because I work for TfL and technically I'm probably not supposed to report this, but I genuinely think something odd happened and I want some perspective.

Back on the 8th of November, I was working late in the maintenance tunnels below King's Cross - the older, less-used sections. About 10:15pm, I was checking some of the historical passages when I heard movement in one of the sealed-off sections. Something large, definitely bipedal by the sound of it, moving quickly.

I didn't see it directly, but I got a very brief glimpse of something dark and substantial moving past a doorway about fifteen feet away. It moved too fast for me to identify it, but it was definitely not human-sized. Could've been a homeless person or an animal that got into the tunnels, but the size and movement pattern didn't match anything ordinary.

I reported it to my supervisor and they basically told me to keep quiet about it, which made me think they might know something. Haven't heard anything else about it since, but I'm still puzzled. Has anyone else heard rumours of unusual activity in the Underground?

This is interesting because the Underground has some genuinely cryptozoological reputation. There's been decades of anecdotal reports about 'tunnel creatures' - usually dismissed as rats or people, but the scale discrepancies sometimes suggest something else. The fact that your supervisor wanted you to keep quiet is intriguing.

Big rats. The Underground's got some genuinely enormous rats, and in low light conditions, moving quickly, they can look bigger than they actually are. Also, sound travels weirdly in tunnels, which could amplify the impression of something larger. That would be my guess.

TfL absolutely does suppress reports of unusual findings in the tunnels. They don't want public panic about 'whatever lives under London.' I've heard this from multiple sources. Whether there's anything genuinely anomalous or just unusual fauna, the official line is always to keep it quiet.

Have you considered whether it might've been a sewage worker from a different section? Or someone from a different organisation working in the tunnels? King's Cross has work happening constantly, and different teams don't always know what the others are doing.

I'd love to know which specific section this was. The older tunnels under King's Cross are supposedly extensive - some connected to historical stations that don't exist anymore. That could explain why a supervisor wouldn't want to investigate too closely. Might be asbestos or structural concerns they don't want documented.