Surrey Police are appealing for help in finding a man who has not been seen since Sunday evening (7 January).
David Luck, 74, from Horley, is described as vulnerable and officers are concerned for his welfare.
He is white, 5ft 8 tall, of a slim build, with grey balding hair and blue eyes. Police add that he wears glasses and potentially has all his lower teeth missing.
David travels by bus and train and has been described as a trainspotter.
Surrey Police also have a number of enquiries under way with their colleagues at Sussex Police and the British Transport Police.
Anyone who has seen David, or has any information as to his whereabouts, should contact Surrey Police on 101, quoting incident reference PR/P18005872.