A less-obvious part of the Cambridge South work is this small addition (new track on left of photo) to the southern throat of Cambridge station (also known as Cambridge South Junction). It's a new mini-route out of the station, called the Hills Road Spur. (1/4)
The existing headshunt is being extended to feed into the up main, allowing 'up' (to London) departures from p8 in parallel with 'down' (from London) arrivals at p7, which is currently not possible. (2/4)
P7 often acts as a terminating platform for trains from London, and once the new mini-route is commissioned, it can do this independently of up trains through p8. So, extra timetabling flexibility and more resilience too. (3/4)