Having thought long and hard about the matter, I have decided not to respond - for the very reasons Arfur makes.
My comments concerned the totally normal use of 23° flap when manoeuvring the Hunter and were confirmed by others with far more experience on the type.
Hydrobooster jackstall only occurs above M0.9 with flap extended; that would equate to around 590KIAS at low level and Andy's aircraft was flying at nowhere near such a speed.
And that's all I have to say about that.