Liam, I guess our recollections are a little hazy. Firstly, there is no significant 'hump' in the runway at the centre intersection. There was a lot of work in progress at the time and the runway lights were being used as one of the methods of alerting the workforce to aircraft movements; this was a difference to the normal procedure whereby all vehicles would ordinarily call on management radio to cross the runway.
Anyway, our intrepid air traffic assistant, for whatever reason, forgets the procedures and goes flying across the central intersection (aptly named Charlie) without any ATC clearance, not noticing that the runway lights were on (the "get off the runway" message) and gets rather close to Timmy. There are various assessments as to how 'close' things got - suffice to say it was close enough to twitch many a sphincter. The Tristar crew do a sterling job, depart to the SW for an underwear change and eventually come back with evidence of a significant tailscrape.
The witch hunt never actually came up with a categorical reason why SAC F'witt did what he did. Unfortunately, a local procedure was then introduced whereby the centre intersection lights were left on red and changed by ATC to green whenever they wanted to clear a vehicle to cross. In HF terms this was (is?) absolute madness as these lights are operated in the opposite sense to any other set of ATC controlled traffic lights. Some years later I observed a light aircraft land, a vehicle call to cross at the centre and the controller automatically switch the centre lights from red to green (whilst the aircraft was still on the runway) as he had been 'conditioned' to operate in this way.
As for OC 101 playing chicken with the same lights................