"Peterborough even, at a push. It never used to be, but it is now."
I very much agree that it is commuter belt all the way up, but it's not new. I was certainly commuting from Peterborough to London 27 years ago. Even back then there were a lot of people doing that (mostly men though).
Back then the railway had only recently been privatised (it was British Rail up until 30 years ago). Those that could afford it went non-stop with GNER (nowadays LNER).
Others, like myself, went on the slower Thameslink trains that stop at other commuter towns like Huntingdon, St Neots and Biggleswade where more commuters would get on.
Or, you could end on the stopping train that stops at literally every station along the way, including Sandy, (and even Finsbury Park) on it's way to Kings Cross.
Sorry, totally off-topic.