So why wasn't it fixed before the Hawk entered service?
Hey BEags come on. You probably know the answer to that question better than most who post here.
I refuse to be drawn into more specifics about this issue than what follows - not because I am afraid of limiting my career (ha!) but just because I have better things to get on with today.
In those days there was something called GFE (Government furnished equipment) which was often specified by the customer as having to be fitted.
The T1 was a Hawker aeroplane (pre BAe) and the chaps in that org on a daily basis really did do their best for the user (not the customer) but sometimes they had no control over events.
A2E2 was the clearance to service authority not Hawkers.
Over the years many in A2E2 did not always agree what they were told to clear.
Neville Shute (who knew a thing or two about the aviation industry and life) had one of his characters (an RAE boffin) say that you could not maintain your professional integrity as an engineer in the aircraft business unless you had a private income.
I had a UK civilian (1 or 2 star) project director write to my company and formally complain that my job was to fly aeroplanes and not to publicly express views that went against his procurement policy over a bit of kit for the GR5 at his meeting in the US (would you believe that kit also told you which way the aircraft was pointed). Despite the subsequent unpleasantness I was much chuffed when on that occasion the technical case I made won the day. In those days technical merit did not always win out over political expediency.