Vlad...
Is it clear the crew understood e.g. via read back, the "GA" instruction?
Certainly "up the road" a late landing clearance is preceded by the ATCO starting a transmission (to prevent others cutting in), speaking slowly, and giving e.g. the wind. Once you hear this you are "anticipating" a "Clear Land", and understand if the ATCO is just waiting until the aircraft ahead has technically vacated.
The trouble with this is if the ATCO changes his mind (as appears to have happened here) he thinks he has clearly told the aircraft to "GA" - but at that late stage there can be so many audio alerts (e.g. Rad Alt calls, "Minimums", "Retard") you don't clearly here what has been said.
Rather worrying to see NATS decide to publicise this and "get their side of the story" in via the press, rather than let an MOR/ASR process learn the lessons
