 Shannon was discharged from the RAAF as a squadron leader on 15 December 1945. He remained in England and became an executive with Shell and later Cunard. Shannon no longer flew after the war, but did like to drive fast cars. He also served as chairman of the No. 617 Squadron Association, helping to raise funds for the Dambusters memorial at Woodhall Spa near RAF Scampton. On 8 April 1993, shortly before a planned fiftieth anniversary reunion of surviving Dambusters, he died at his home in Sydenham, South London, aged seventy. He was survived by his second wife Eyke and his daughter by Ann. On 17 May 2008, the sixty-fifth anniversary of the Dambusters raid, a memorial to Shannon and two other South Australians who took part in the mission, bomb aimers Fred Spafford and Bob Hay, was unveiled in Adelaide in the presence of the airmen's families. In July 2009 Shannon's daughter Nikki made his medals, uniform, and logbook available to the Australian War Memorial in Canberra, for long-term display.
