Thanks - they just managed to squeeze us in. It was indeed coach L but that was the London end of the rear unit.That is helpful, but by way of a guarantee it's whichever end first class vehicle doesn't have reservations in - hope that helps!
Glad you managed. Unusual for it to be in the rear unit heading to London, guess something went wrong in Swansea/Carmarthen. That being said I do check the platform display when joining at intermediate stations to check where L is… and then watch the train as it comes in just in case!Thanks - they just managed to squeeze us in. It was indeed coach L but that was the London end of the rear unit.