[mannykannot]

Every jet engine, barring the first few independently-developed ones, was derived from predecessors, so this may mean something significant, or it may not.

The TSR-2 never went into production, which raises the question of which (if any) of these projects was riding the coattails of the other. I accept that the total bill written-off could have been reduced if there was some R&D cost-sharing, but, as the TSR-2 was a ground-hugging strike aircraft intended for relatively short European-theater missions as opposed to intercontinental flight, I suspect the issues that needed R&D were quite different for the two aircraft.

As for supersonic interceptors, the missiles that rendered the high-altitude supersonic bomber irrelevant did the same for the interceptor. The only supersonic interceptor both developed and deployed by the UK was the EE/BAC Lightning, the predecessor of the TSR-2. At least, unlike the TSR-2, this airplane was put into production and into service.

[dboreham]

The two engines were designed and built at the same plant (Filton: I lived a few 100 yards from the fence in the 80s -- noisy at times). So there was significant benefit from the previous military projects even if only that they didn't need to build a new plant, test stands, and staff up a new design team.