A 77-year-old man has been arrested in connection with the 1985 killing of exiled Seychelles politician Gerard Hoarau.
The dissident was gunned down on his doorstep in Greencourt Avenue, Edgware, north London, on November 29, 1985.
He was shot with a Sterling sub-machine gun.
Scotland Yard announced yesterday that a suspect had been arrested at 9.50am in Antrim, Northern Ireland, on suspicion of conspiracy to murder.
Officers from the Police Service of Northern Ireland assisted the operation and are now helping search his property.
Several individuals were previously been arrested in connection with the 1985 assassination, but no charges followed.
Three people were convicted of perverting the course of justice by meddling with the investigation in 1986, police said.
The trail then went cold for decades, prompting a review in 2016 from which fresh lines of inquiry were established, according to the force.
The man arrested yesterday had not previously been arrested as part of the investigation.
He has been transported to a police station in south London for questioning.