Cawthorn worked well with Peter Fleming and the ultra secret double agent network at GSI(d), the network faced earlier in the war at Rangoon. Unlike Ormonde Hunter, a previous chief he was entirely sympathetic to the agency's aims. Cawthorn had none of these suspicions about the counter-intelligence activity. He was brought to London in March 1943 to discuss double-agents with MI5, before leaving with Churchill's team for the Trident Conference (19-30 May 1943), where he was one of the four-man British negotiating team. Hunter joined them on 28 May to sketch an outline for Operation Saucy, a plan for Japanese deception. The full plan was fleshed out at New Delhi with Fleming, which they dubbed Ramshorn. It was devised as a tactic to divert the Japanese Air Force away from MacArthur's main forces, but predictably John Bevan back in London shot the plan down in flames. Cawthorne had been too ambitious; all that they could do was create 'an illusion of an amphibious landing'.