The first X-rays produced in Britain have emerged after decades forgotten in a box of files - and are set to sell for £20,000.

They were produced by Victorian inventor Alan Swinton, weeks after a German scientist beat him as the first to use the radiation imaging process in 1886.

But they were then squirrelled away in a box until collector Roy Davids uncovered them in a pile of documents he bought at auction 15 years ago.