Thames Valley Police is asking for the public’s help to find absconder Malcolm Millman, who has links to Cleveland.
Officers would like to speak to anyone who has seen him or recognises someone matching his description.
Millman was convicted of rape in 1996 and poses a risk specifically to woman and girls.
Thames Valley Police believes he could be violent and he has previously threatened his victims with a weapon.
Members of the public should not approach him but should contact Thames Valley Police on 101.
He was last seen at Manchester Airport Railway Station on Monday at around 12.30pm. He is not believed to have boarded a plane and he does not have a passport.
Millman absconded during a day visit to a monastery in St Margarets, Great Gaddesden, Hemel Hempstead, at about 2pm on October 24.
He failed to return to Chadwick Lodge, a secure facility in Chadwick Drive, Eaglestone, Milton Keynes, whose care he was under.
Millman has withdrawn a large cash sum from cash points during the weekend and has been using public transport. He may also be booking into hotels or hostels.
Millman is white, of large build, bald with thinning brown hair on the sides, and brown eyes.
He was last seen wearing a brown jacket, purple jumper, grey tracksuit bottoms and blue and white trainers. He also uses a walking stick.
Millman has medical conditions including a heart condition and diabetes so he may be seeking medication.
Det Supt Chris Ward from Major Crime, said: “Thames Valley Police needs the public’s help to find Malcolm Millman.We are also working closely with other police forces and organisations to locate him as soon as possible.
“Millman was convicted of rape in 1996 and we believe he poses a potential risk, specifically to woman and girls.
“I want to urge everybody to remain vigilant. If you see this man, please do not approach him but contact the police immediately
“If any member of the public sees Millman, do not approach him, but call Thames Valley Police on 101 or 999.
Or if you have any information, no matter how small the detail about Millman’s whereabouts then please call police via 101.”
Millman is also known by the following names: Richard Simon Barber, Michael Geoffrey Newman, and Raymond Pilkington.
He has links to Kent, Warwickshire, London, Cleveland and North Wales.