I'm not surprised, in total we had 7.5 hours of riding time, the way home was (for me at least) tiring for the last 50miles and sheer pain for the last 25-30miles.
first time any of us had done that kind of distance, and first time i'd done any kind of distance on that seat (stupidly).
I am lucky that might bike is superbly fitted and the saddle ideal. The slight redness I saw yesterday has gone with sudacreme.
I'm surprised you didn't pass me on the way back to London. I was so slow on Sunday. Took more than two hours less today.