That 20 minutes can be a giveaway though. I can't think of another 20 minute walk I have encountered, maybe Kings Cross to Euston but I think when it was Stafford, I was routed Kings Cross to Euston as a 5 minute tube journey.
I've switched to Ely as my starting station. Kings Cross is 1:15 away, Peterborough 40 minutes away, Norwich is 50 minutes away and I can go from there. I used Cambridge for a while until I realised that both Kings Cross and Peterborough were 50 minutes away, although it's usually pretty obvious that you're going through London. But there aren't many directions to go from Ely, and each timing to a major interchange is unique.
It's served me pretty well in the last week, since one answer was actually Ely and another was Inverness (7 hours on one train from Peterborough!)