Blink Bonny wrote:
" .... I think in fairness the AWS system had been in development for a few years at that point and this disaster simply brought the timetable forwards. .... "
Setting aside the GWR's great achievements with their electro-mechanical, audible-only ATC system, widespread at least by the end of The Great War, and experiments by other companies, including the NER's Relio-Stop, the inductive (no mechanical track equipment/train contact), audio-visual method, I think began as the 'Strowger-Hudd system trialled on the LT&SR route, which was IIRC the prototype for our now-standard AWS, and I would guess was in place in the late 1940s.
I do recall reading that an extensive trial of AWS was conducted (on the Fast lines only I think) between New Barnet and Huntingdon, commencing I think in 1951.
So It seems quite possible that at the time of 'Harrow', AWS may well not yet have been formally accepted for national adoption.
Incidentally, the GWR system carried on well into the modern image "British Rail" period, with quite a lot of traction (e.g., a number of Class 37s) having to be dual-fitted for inter-BR(W) / rest of the country running.
IIRC the last GW system installations were not replaced by BR standard AWS until at least 1983, and I've a feeling there were still some other BR areas which weren't AWS-equipped at all until around the same era.