A man has been arrested on suspicion of conspiring to murder Pc Yvonne Fletcher, who was shot dead outside the Libyan embassy in London 31 years ago.
The Libyan suspect, in his 50s,was held at a location in south east England in what police described as "the first significant arrest" of the investigation into the 25-year-old officer's killing in 1984.
Detectives have also arrested a man and a woman on suspicion of money laundering.