At the time, from my West Upper vantage point I'd have called it a foul. Having now seen it on the replays its clear that its a perfectly legal challenge.
I can't believe it stood. When I saw the keeper floundering on the floor, I was waiting for the whistle. I couldn't see many complaining Norwich fans either. In these days of keepers having more protection than ever before, amazed it wasn't a free kick.