Latest copy of Aircraft magazine has a fascinating article by AVM Topp/ Torp?? who was the CO at the time and how he went about getting approval to do it, and also the problems involved with power settings etc, as some of the jets would still be ascending when others were descending..... good read
Not a bad mag either, this is the one that it is in.
Aircraft Magazine
BACK TO BLACK
Of all the RAF’s Hunter aerobatic teams, the Black Arrows achieved the most legendary status — thanks not least to that famous 22-aircraft Farnborough loop