Sunday 24th November 4.45pm.
I figured that a Sunday afternoon in the weeks before Christmas was exactly the kind of peak time Transport for London suggest you avoid using Covent Garden station so despite being on the Plaza I opted to walk to Holborn instead. It's only two stops from King's Cross, neither of them very long, and on another day I might have been tempted just to walk the whole way instead.
The outside is one of those grand but quite restrained entrances, but inside is the usual rabbit warren of tunnels and stairs to get you down to platform level, with so many twists and turns it's hard to know quite where you've ended up. But the platforms for the Piccadilly line at least have been smartened up with metal cladding on the walls instead of tiling, with pictures inspired by the British Museum (which is very nearby), including wrestling naked Greeks which I stupidly forgot to take a picture of.
Wikipedia entry here.