Great Western Coffee Shop

I got caught up in the fun caused by a broken down train at Reading West (I think) yesterday evening. My train, the 16:06 Paddington - Penzance (non-stop Reading Taunton), got diverted via Bath and Bristol; in the end I was only 30 minutes late into Taunton so not too bad. Once we left Reading the diversion only added about 15 minutes to the normal Reading - Taunton non stop time, we were lucky not to get held up at all going through Bristol or the quite common 'stuck behind a stopping train' routine between Bristol and Taunton.

I got diverted on the way home a couple of weeks back and that time we were diverted via Melksham and Westbury but that diversion added about 40 minutes to the Reading - Taunton time; however on that occasion I think a lot of that time was eaten by having to wait to get onto the single line section via Melksham.

All this got me wondering; how are the routes for diversions like these decided? Is it purely on what  paths are available through where ? Last night, when we went through Chippenham I assumed we would be going via Melksham as they wouldn't want an extra train cluttering up Bristol. When we passed Bath I was then wondering why we hadn't gone straight to Bristol Parkway from Swindon  and then south west.

Answers on a postcard!

Drivers/TM's route knowledge is also a factor.

You may've answered your own question.

Going via Bristol Parkway may not have been possible due to pathing constraints.

Are both the driver and TM required to have route knowledge, or would just the driver signing the route be satisfactory?

Both, as both are involved in the protection of the train in an emergency, both have roles to play in any out of course situations such as single line working and the guard will need to know the location of stations en-route in case the train gets stopped out of course.

I would assume all drivers covering Exeter - Paddington would have route knowledge via Bath as there are two or three trains a day that are timetabled to take that route.  Presumably route knowledge via Parkway is not standard.

Certainly TM's and Drivers working out of Exeter depot learn via Bristol Parkway-Swindon (Hullavington) as a diversion, I would assume Plymouth crews learn it too.

Also, I was travelling to London as a passenger on the 1358 EXD-PAD service which was diverted from Westbury to Reading via Melksham, so given the single line, they may have kept the single line for up-London services.