The first Carlo Crivelli show in the UK compares his games of illusionism to those of Magritte – and Surrealist touches abound, says Laura Gascoigne

Certain standards are demanded of civic dignitaries; at very least, they must maintain dignity. So when in 1484 the attendant of a magistrate in the town of Ascoli Piceno was seen carrying a vegetable marrow while on duty, he was punished for bringing his office into disrepute.

Two years earlier Ascoli Piceno, which is in the Marche region of what is now Italy, had been officially granted libertas ­ecclesiastica by Sixtus IV, and the comune chose to celebrate the event on the Feast of the Annunciation – which was the day news of papal approval first arrived from Rome. An annual procession to the Church of Santissima Annunziata was duly established for each 25 March, and an altarpiece was commissioned from the leading artist of the region, the Venetian-born Carlo Crivelli.