How far is it from Euston Railway station to St Pancras?
It’s about 5-10 minutes walk – just come out of Euston onto the main road and turn left. You can take a tube, but to be honest you’d be walking just about as far – from the rail platforms, down into the tube station, along loads of tunnels, one stop on the tube, then all the way back up again at St Pancras. I disagree with Loopy Lu – it’s perfectly fine to do this with a suitcase, especially the type you describe. It’s a busy road so even at night you wouldn’t have any security problems, and it’s a straight road with no hills.