Twitter for SWtrains says its due to planned works in Wimbledon. Which we don’t even stop at.  
So I got on the local. It’s more spacious but a bit more like a bus than a train.  I wonder why it can route around Wimbledon but the Salisbury train couldn’t.

Reminded me that I was planning on doing this regular like. Getting off the train in Basingstoke and moving over to another spacious train for the second half of the trip.