Departed Plymouth 6 minutes late, arrived at Totnes 121 late. Not bad. As of 04:48 it's currently in the Castle Cary area 144 minutes late.
TRUST delay attribution is
“Update 23:33. 1A40 TPWS Probs Plymouth, Plymouth signaller advises. Train now stationary after departing. Wtg further info. 1A40 returned to Plymouth pending events. Update 01:30, 2 HST power cars off Laira TMD to work train forward. On the move 121' late.”.
A further 46 minute delay was incurred at Exeter St Davids whilst the HST power cars were swapped with the loco off 1C99 which is now working the train forward to Paddington.
The train is also booked via Honiton tonight but I'm not too up on that area so I don't know if that's a regular route for 1A40. That should answer your question.