From a a further out perspective the peak semi-fasts running to/from Cambridge is is good. I don't travel in the morning peak these days but I do expect to be using the 1724/1754/1824/1854 departures from Kings Cross in the evening to travel through to Cambridge.
Why on earth would you want to do that? A considerable number of extra stops when there's 2tph fast. Note also that two of these services will be formed of 700/0, the other two 8/387.
The 1718/1748/1818 will be 12 cars. That solution has already happened.
Does Cambridge really need further capacity on top of this?
The number of passengers doing this is small: Royston/Baldock-Welwyn GC/Hatfield one way flows are all about 3-4k. And they haven't been completely forgotten with 0703 Royston-Kings Cross in the morning and 1757 Kings Cross-Royston in the evening.
The morning one may be useful, but I'm not sure who the evening one is aimed at.
I've had a look at the whole thing. I make it
25 379 diagrams (from 30)
8 387 diagrams (from 13)
Essentially 8 700/0 diagrams (though slightly complicated as there's a small amount of crossover onto the Sevenoaks services)
1 700/1 diagram.
I'll hopefully have a more detailed look at a later date and confirm the above.
As far as I can see, everything north of Cambridge is 379. Contrary to rumours, the 387s aren't confined to peak-only work. They work a proportion of the stopping services throughout the day, and some of the peak extras.
I presume the spare 387s could work the 700/1 Peterborough out-and-back working if required.