The crime of James Legg, a Chelsea pensioner who murdered a fellow pensioner more than two centuries ago, might well have been forgotten long ago had he not, unknowingly, participated postmortem in a bizarre scientific experiment.

Instead, his story, and a plaster cast of the 73-year-old's corpse flayed to the muscle, will form the centrepiece of an exhibition on medical ethics and practices in bygone London. Legg's immortality in art owes everything to the efforts in 1801 of sculptor Thomas Bank, and artists Benjamin West and Richard Crossway, to demonstrate most depictions of the crucifixion of Christ were anatomically incorrect.

Aside from stringing up a live victim, the best possible solution would seem to be to acquire one freshly dead.

At the time, as the study and teaching of anatomy became increasingly popular, the only legal source of corpses were those of executed prisoners. Demand, though, far exceeded supply, leading to brisk business in the gruesome trade of bodysnatching, where gangs of what were known as resurrection men stole corpses from the capital's cemeteries to sell to anatomist surgeons.

It was not only the surgeons who were interested in the dead bodies. Anatomy classes were also offered at the Royal Academy of Arts, and many artists forged relationships with surgeon-anatomists.

So, it was to Joseph Constantine Carpue, a well-known surgeon, that Banks and the artists turned for help.

An opportunity presented itself when Carpue was called to the Chelsea hospital after Legg had apparently dispatched one of his fellow pensioners with a gun. He was sentenced to death by hanging, and taken to the gallows.

Immediately after the execution, his still-warm body was taken by Carpue and Banks and hung from a cross. After letting it settle into position, it was then flayed to remove all the skin before Banks made a cast of it, which the Royal Academy retains, occasionally lending it to exhibitions.

Now the plaster cast is going on display at the Museum of London as part of the exhibition Doctors, Dissection and Resurrection Men, which opens on 19 October.

Jelena Beklavac, curator of Human Osteology at the Museum of London, said: "It is a privilege to have the James Legg cast on display. Looking at James is an absorbing and poignant experience and I am certain visitors will be struck by his presence in the exhibition. James underlines our continued fascination with all things anatomical."