Correct whilst some HSTs run through Frome there is a Frome to Westbury HST that then runs ECS to the Marsh anyway.
There is or was a couple of services that ran from Frome - Westbury early morning/late at night. The ECS turn for one of the mornings used to be funny, Left Westbury for Heywood Road Junction, change ends then ran over the Westbury avoider to Fairwood then over to Frome!
Radyr - Coryton is close to each other, how easy is it to get between the two? Looked at google maps once and there is an annoying river between the two and the bridge to get across looked like it was miles to the north! Looked like to walk it might have taken the same time as the train does
Whilst we are on shortest schedules, any short ECS turns that could win this too? There is a lot of yards/depots to stations that are short, so maybe shortest ECS between stations? Westbury to Frome or to Warminster is one...any others that could be shorter?