Whichever, I don't believe B Cal ran their mail One-Elevens to East Midlands, but were on Gatwick to Edinburgh. The operation later passed to British Midland and operated from Heathrow, where it was exempted from the night quota. It used to come in from Edinburgh after midnight, on fine nights making a decidedly visual approach.
I was driving inwards on the M4 at such a time, and saw lights in the sky to my left. At first I thought it was for old Runway 23, but in fact was fractionally further along, a BMA DC9, which made a tight turn down onto 27R (possibly still 28R). Discussed with someone here a while ago, who remembered the empty skies fun flying of that flight.