The 150s cycle through the Cornish branches eventually ending back at Exeter.
Long Rock sends one unit to St Ives. two units to Falmouth which split to make up the two train service.
Having been driving past Truro daily the last three days, I've noticed a two car (150?) parked in the Truro siding all day it seems.
It's possible it had done a run in between my frequent passing but unlikely from the positioning.
Was the Falmouth branch down to one unit for 3 days?