Thanks, Aviate 1138, that is the one. I only ever saw one flying, and that was when I was spectating at Farnborough. One appeared to be climbing out of/over Blackbushe, and the noise, even at that distance, was unlike any other aircraft I had heard. Interesting to read about the Thunderstreak slung underneath. There were about 4[?] built under the FICON programme. I saw one in the museum at Chino, CA. It has a large hook ahead of the cockpit, and otherwise looks like a standard F84F, but with an anhedral tailplane.