Erik Inglis, 42, who is also known as Simon Pascall, has been sleeping rough and was last seen last seen at around midday at Datchet Road, Home Park, Windsor. He also has links to Ascot, Slough and Oxford.
PC Tom Hughes-Parry, the officer dealing with the case, said: "We would urge Erik to get in touch. We would ask that anyone who thinks they recognise Erik to get in touch with the police as soon as possible."
Mr Inglis is of medium build, 5ft 7ins, with brown shoulder-length hair and he was last seen wearing a long, thick, grey trench coat, jeans, boots, and a grey, round hat, possibly with feathers. He had a safety pin in his right eyebrow and a bar through his left eyebrow.
Anyone with information is asked to contact 24-hour Police Enquiry Centre on 101 or the charity Crimestoppers anonymously via 0800 555 111 or www.crimestoppers-uk.org