Putting aside the malevolent purpose, the defence industry can come up with astonishing feats of engineering. Russia’s fifth-gen fighter plane the ‘Felon’ is such a marvel, but will it become extinct before it flies the roost?

Since the days of the Cold War, Russia’s defence industry has been part war machine, part confidence trick.

“There is a general pattern that the hype of Russian weapons systems hasn’t been challenged, and so has generally been believed,” says Sir Keir Giles, Russia expert at Chatham House and author of forthcoming book Who Will Defend Europe? “And that’s happened with more or less any Russian weapon system you care to name, because they’ve been operating in this unopposed environment – unless and until they bump up against a determined and well-equipped adversary. That’s when it comes unstuck.”

In 1967, American spy satellites photographed a new, top-secret aircraft on the runway at the Ramenskoye (now Zhukovsky) airfield in Russia – an infamous testing ground for...