The mystery was solved when a police officer pushed the back of one of the library's bookshelves, revealing a small secret room and a rope ladder that eventually led to the convent's workshop. With the authorities lying in wait, the thief – a mechanical engineering teacher with a penchant for Latin – was caught. He'd found a lost map, reportedly pictured here, in the public archives that showed the forgotten space. Having stolen the books because of his passion for the ancient artefacts, they were all safely returned.

The most amazing secret spaces hiding in stately homes