Seriously it was a requirement of the spec that it attained Mach 1.6 which it did eventually after a struggle, then was binned as it had shown it had attained the brief, various mods were introduced, I didn't realise the step in the elevon was to reduce strain on the actuators and it was smoothed out by about 1 inch during testing, the M was going to eventually have a different wing. Various differences included beefed up hook, straight longer stroke main legs and twin nose wheels, beefed up fuselage with fuselage mounted catapult attachments. It also said all Jags had the ability to carry centre line refuelling pods, did ours?