It must be a bit of a push on the likes of a LHR-MAN shuttle run though? Have been on such flights and they tend to last about 30-35 minutes takeoff to touchdown. Flying at the lower levels (FL180/190) must mean more r/t work and T/C to T/D must be about 6 or 7 minutes at most?
Is it feasable to do the departure brief and approach brief on the stand @ LHR in those circumstances?