Ah T1 Domestic.... around mid '80' s during shuttle days would arr on the underground and up the long escalator to Domestic far top left, through the 5 desks, no queue always fully manned and from the window the long line of Trident and Vanguard tails with BMA various types, and sometimes the SAA 747 on the right with occasional VC10's parked up out the way. Through security, briefcase only and down the pier. Exotic destinations, Leeds, Manchester, Aberdeen and into the Inverness flight. Fri evening up Monday down. Did this for some 3 months all paid for by Aunt Betty.
However back to the OP Question. At the check in desks I remember a circular spiral chute to ground level for the bags to go down to the loaders