Elizabeth Line train on the GWML Down Main (rather than Down Relief) 24/01

[Jamiescott1]

I'm crawling along on a "fast" service on the mains approaching Southall and looked on RTT to see possible reason for the slow service and it appears a stopping EL service to reading is on the main line delaying all the fast gwr trains.
Anyone know why this one train (9R48) is on the mains

 

[aliceh]

My guess is something to do with 9H46 ahead of it, which spent 13 minutes at Ealing Broadway. I suspect 9R48 was routed onto the mains to overtake it.

 

[FuzzyDuck]

It's currently on the down relief approaching Maindehead.

 

[TFN]

Yes, @aliceh was correct. It was routed on to the mains before Ealing Broadway because 9H46 had an issue at Ealing (I believe failed to transition). It was routed back on to the reliefs after Hayes.