I seem to recall that Capt. Bruce Morgan got a "nine" in (pre-extension) during stiff favourable winds due to Teesside being out. It was a change for Leeds winds to work to advantage.
Nines were not unknown before the runway extension. Martinair dropped in occasionally on charters every now and then. IIRC some were ship's crews bound for Hull. Even if HUY could have handled a 9 at time it was still a few years before the Humber bridge. Quicker by the M62 than ambling through lanes from Kirmington to Barton on Humber and then waiting for the ferry, DEPV Faringford, to waddle over.
There's also an 'on this day' moment here. 13 November 1976 was one of those days when much of the country was in fog. Low lying stuff so LBA for once was out of it. May have been a couple of prop diversions but the star was an Aviaco DC-9, EC-CTS. Out of either Las Palmas or Tenerife for Birmingham.
Outbound load was only about 50 and he went direct. Used rather more runway than the Britt 737s, took 33 (oddly in near still air) and rotated around the 10/28 intersection.