The armoured plant-eater, who roamed North America around 150 million years ago, is sure to wow visitors as she joins ‘Dippy’ the Diplodocus, whose massive replica skeleton has stood in the museum’s central Hintze hall since 1905.

Sophie’s skeleton is genuine and is also an incredible 90 per cent complete – although replica parts will still replace the skull and a few other delicate bones which have been carefully stored away.

Professor Paul Barrett, the museum’s chief dinosaur scientist, told the Daily Mail: “Stegosaurus fossil finds are rare. This one inspires genuine wonder. Having the world’s most complete example here for research means we can begin to uncover the secrets behind the evolution and behaviour of this intriguing dinosaur species.”

The stegosaurus is an iconic dinosaur famed for the row of huge flesh-covered plates along its spine and the fierce-looking spikes near the tip of its tail which would have been used to sweep would-be predators aside.

It has also been traditionally portrayed as a dim-witted dinosaur – despite its huge body it had only a tiny head containing a brain the size of an walnut.

The sex of the Natural History Museum’s stegosaurus is not actually known, but the specimen has been named Sophie after the daughter of the hedge fund manager whose major donation made her acquisition possible.

Stegosaurus skeletons are scarce – there are only half-a-dozen known examples, most of them incomplete and squashed flat. Sophie’s 360 fossilised bones were discovered by palaeontologist Bob Simon at Red Canyon Ranch, in Wyoming, in 2003. She was bought with the help of 70 donations after Professor Barrett found her at an international fossil fair in the United States.

Sophie, who lived in the Late Jurassic period, is thought to have been a young adult when she died. At 18ft long and nearly 10 feet tall she is still relatively small compared with larger specimens which measured up to 29ft in length. She now takes pride of place in the museum’s Earth Hall.

Scientists have already laser-scanned the bones and put them through a CT scanner to create computer models showing what Sophie might have looked like. It is hoped that modern research technology may help them solve some of the mysteries surrounding the stegosaurus – not least the function of those fearsome plates along Sophie’s back. One theory is that rather than being used for defence purposes they acted as huge solar panels to help provide body heat.