Very ancient history... but
In the late 60s & early 70s for the November/December surge BA used to charter in cargo capacity for the LHR-HKG-LHR route, which was strict cabotage in those days meant that was almost impossible to get anyone other than a British airline to perform the charter.
This meant quite frequently would be a British Midland B707 ... in full pax version, with the cargo loose-loaded over the seats.
Used to take 24-48 hours to load & 24-48 hours to unload....
'twere a right pig - usually customs had cleared & released the cargo before we'd even got it off the ac.... cue lots of very upset truckies spending hours & hours & hours sitting in the truck park ....
(They weren't getting "OT")