Great Western Coffee Shop

I'm curious as to why the TW is replaced by buses today due to the block at Swindon. There are services at both ends of the core route (Chippenham and Trowbridge), and no diverted services over the line, so a curtailed service from Chippenham to Westbury is surely possible?  What am I missing?

Only a guess, but with a Chippenham-Bristol shuttle running and laying over for 15 minutes an hour at Chippenham on platform 2 you might have congestion problems.

Due to the Swindon Blockade for the resignalling. With London to Bristol and South Wales Trains being diverted From Reading via Westbury and Bath the line from Westbury to Bathampton Jn must be a tad busy.  Trying to fit even a Trowbridge Chippenham Service in would be a challenge I think. 

I don't know the answer on this one.  But thinking about it, if the train service ran at (roughly) the normal times, it would be a long layover at Chippenham ((but then 2 trains can reverse there at the same time)) ; if the train did an out-and-back from Westbury, you're potentially looking at a lot of shunting and re-platforming there.    And as noted there's quite a bit of extra traffic from the Westbury area to Bradford Junction today and tomorrow - unlike some other weekends, it's not just the London to Bristol trains, but London to South Wales too.    I would also venture to suggest that a lot of traffic on trains coming up from Westbury into Chippenham on a typical Saturday usually stays on the train to Swindon (much more than on a Monday to Friday) and with all these things together the balance was probably to a decision that it's best to do it with buses.  Not thrilled, but not an issue top of the "critical" list either.