Oliver McAfee was supposed to be home in time for Christmas 2017. But the 29-year-old landscape gardener, originally from Dromore in Northern Ireland’s County Down, hasn’t been seen since 21 November 2017.

McAfee had been cycling along the Israel National Trail, near the desert city of Mitzpe Ramon, before he vanished. His bicycle and tent were found two months later in the Ramon crater in the southern part of Israel. Travellers have since handed in his wallet, keys, and computer tablet discovered along the trail.

Media outlets were quick to raise the possibility of Jerusalem syndrome – a psychotic state (or a break from reality) often linked to religious experiences. Sufferers become paranoid. They see and hear things that aren’t there. They become possessed and obsessed. And sometimes, they disappear.

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At the turn of the millennium, doctors from Israel’s Kfer Shaul Mental Health Centre reported seeing around 100 tourists a year with the syndrome (40 of whom needed hospital admission), most commonly Christians but also some Jews, and a smaller number of Muslims. Jerusalem syndrome was a form of psychosis, they wrote in the British Journal of Psychiatry, in a city that “conjures up a sense of the holy, the historical and the heavenly”.