I imagine you have delved in to the three D H 108's that were built, a fair bit has been written about them, and a lot learned after Geoffrey de Havilland was killed when it broke into pieces in the Thames Estuary.
The 108 does seem to have been a remarkable aeroplane, and perhaps a little outside the complete understanding of its ability or otherwise. Although, John Derry seems to have made some remarkable discoveries about the 108 and, indeed, with very careful checks, also discovered that he had achieved Mach 1.0.
But the aeroplane did not always maintain controlled flight and must have been a nightmare throughout the envelope. All three crashed but John Derry received a Gold Medal connected with the 108 for achievements in the air.
Where to next.................................?