I disagree with you re. useless as a measure of speed, I worked on Lightnings for five years, their top speed was mach 2.1
And again I shall make my point: How fast is Mach 2.1?
About 1,600 MPH at sea level.
Because your Lightning could do Mach 2.1 at sea level.
Yes it could, albeit a bit bumpy, on test with the TSR2 as they went through the sound barrier at low level, the Lightning was buffeting about all over the place, in comparison the jockey in the TSR2 hardly noticed a thing. But lets not dwell on the past and how the Labour party sunk what was one of the most high tech A/C of its day and would have sold around the world.