A very nice, quiet room in what appears to be a small boarding house a few minutes' walk from St Pancras International, the Crick Institute, and the British Library (which is totally worth a visit). Small, well-equipped en suite toilet and shower. On check-in, you will get a key and a fob; use the fob to open the gate into the area. The key is for the building.
Although we met a couple of the other visitors, we never heard them from our room.
Big plus: access to the common room, which has biscuits, a well-stocked fridge with croissants, coffee, yoghurt, etc. This is a lifesaver for tired travelers.