Engineering work south of Milton Keynes. Even the overnight sleeper trains from Scotland were diverted via Edinburgh into King's Cross.
The Sleeper train starts at Inverness and travels down via Edinburgh. I think it picks up the west coast sleeper in Glasgow and then heads down to KingsX ( I've travelled on both in the past, but the current fares are taking the mickey. I can travel first class and stay a night at a hotel for a similar price.