 After four years in custody he was exchanged, on 24 July 1969, for Soviet spies Morris and Lona Cohen, whose "worknames" (code names) while in the UK were Peter and Helen Kroger, who had been arrested by Special Branch detectives.The Russian authorities only told Brooke he was being sent home 24 hours before he was released back to Britain.Upon his arrival at Heathrow Brooke was surprised by the huge presence of journalists and reporters.