At Heathrow in the old days when we used proper strips and 'Checker' (or 'Seagull' for that matter') entered the runway for inspection (or whatever…) a blocking strip was displayed in the bay. The vehicle thus had 'procedural' occupancy of that runway whether it remained on, or was on/off/back on. Meanwhile it was time to do one's nails or sort out the EG list. It was hardly worth even watching the vehicle whizz on and off, and one should never assume anything anyway in aviation even based on visual observation. It was Checker's runway until such time a 'runway vacated' report was acknowledged at which time it reverted to the runway controller. Runway possession is that of the traffic cleared to use it, ie. whosever strip was in the bay. The ATCO merely manages runway occupancy. Not much different to a locomotive driver on a single rail line being in possession of 'the token' given to him by the signalman really…so why is all this so difficult?