A 19-year-old man has been arrested in connection with the suspected contract killing of an East Sussex businessman.
Ken Harvey, who lived in Brede, near Hastings, was shot as he drove to work.
Sussex Police described today's arrest as a major breakthrough.
Officers swooped on an address in London early this morning.
The suspect was driven to Hastings police station for questioning.
Police search teams were combing two addresses and a stretch of water in the London area the murder weapon and other evidence.
Detective Chief Inspector Reg Hooke, heading the inquiry, described today's action as "a significant step forward".
Mr Harvey was shot at point blank range in his car on August 18.
Police believe the gunmen, who rode up on a motorbike as Mr Harvey sat at traffic lights, were contract killers.
Sussex Police have made extensive inquiries in the London area after learning that the green Kawasaki 750 motorbike used in the shooting had been stolen from Islington, north London, in June.
Police later linked the bike to a Bedford van which may have been used to transport the stolen bike.
Mr Harvey, 44, was shot three times through the window of his Mercedes car when he stopped at crossroads at Cripp's Corner, near Battle.
Two days later doctors switched off Mr Harvey's life support machine.
At the time of the shooting, Mr Harvey, who ran a courier firm and lived with his family in a £300,000 detached house, had been on bail charged with two other men with importing 10kg of cocaine.
He was due to stand trial in December.
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