Earlier this year when working in London I would take the odd post work pint in a pub not far from Earl's Court station. First visit, after having settled in, I experienced that familiarity with the unfamiliar feeling that sometimes pops up in unexpected places, and was struck by the odd feeling that there was something I should know about the place - but just couldn't quite place what it was.
I resisted googling for a few days, wondering if my brain would sort out the issue on its own, but had to give in. The boozer, now called The Pembroke, was once the Coleherne Arms - which, back in the day, was a very well known gay pub and leather bar. Also, a stamping ground for not one, but three serial killers: Dennis Nilsen, Michael Lupo and Colin Ireland (although I think it was only the latter who actually hunted for victims in the Coleherne).
I have no idea how I knew that there was something notable about the place (and serial killers don't generally get blue plaques - so it wouldn't have been that). The most obvious reason would be that I'd clocked the road sign (the pub's address is Old Brompton Road, but it's on the corner with Coleherne Road), however I'm not conscious of doing so, and am not entirely sure I would have got the significance of the name anyway. But I must have picked up on something. Confounding how the brain/memory works.