Spanish police are remaining tight-lipped over what happened to a £12,000-valued watch allegedly stolen by Jay Slater in Tenerife. The 19-year-old, who was confirmed to have died after an autopsy yesterday, had messaged friends in the early hours of the day he vanished to admit to the theft, according to former detective Mark Williams-Thomas. The watch became the centre of a mystery as the search for Slater rumbled on after it emerged that police were looking into a late-night fracas at a nightclub which reportedly erupted after a man said his five-figure-valued Rolex had been stolen. Williams…