Just reiterating what scottishpoet said.

The domestics have a fair amount of extra time built in to the schedule relative to total flight time. 90 minutes for a flight that can be done as quick as 50mins and rarely longer than 70 mins.

BA1475 (GLA 06:45 - LHR 08:15) departed at 07:25 this morning, landed and 08:35 and that was a flight on the longer side after having to do a couple of loops in the hold.