Police have released two images of the man they are seeking over the abduction and rape of two women.
Police said the suspect has a distinctive tattoo of the name “bobbie” on his stomach.
He was seen on CCTV trying to book a room at a hotel in Watford.
It comes as they revealed they had arrested another man on suspicion of conspiracy to rape. The 33-year-old is in custody at a west London police station.
The main suspect, described as white, muscular, aged in his late 20s or early 30s, with a bald head or shaved blond hair and a light-coloured short beard, is thought to have snatched his victims in north London after approaching them in a car.
The first woman was taken from a street in Chingford at 12.30am on Thursday, and the second from another road in Edgware at 12.15pm on Thursday 25 April.
He then drove them to a hotel and tried to book a room at around 1pm but left after being told there were no rooms available.
Both women, aged in their 20s, managed to escape at around 2.30pm after a struggle in Osborne Road, Watford.
Detective Chief Inspector Katherine Goodwin said: “Our investigation into these appalling crimes is making good progress and my team continue to work extremely hard but we urgently need the help of the public to identify and trace this man.”
She said the man is thought to have travelled around north London and Hertfordshire in his car from the early hours of Thursday and may have come into contact with other members of the public.
She added: “Equally he may have abandoned his car somewhere – if an unfamiliar car of this description is now parked on your street, call police straight away.
“We would ask anyone with any information to contact us immediately – if you see the suspect do not approach him but call 999 immediately. If you wish to remain anonymous, call Crimestoppers.
“It is vitally important we catch this man, and while stranger attacks of this nature are thankfully rare, we would urge people to remain vigilant.”
On Saturday police released an image of the car used in the attacks: a silver or grey Ford S-Max people carrier, with false registration plates.