Siddon is recorded as the most successful comprehensive land claim negotiator in Canadian history. When fellow British Columbian and ally Kim Campbell became PC leader and prime minister in 1993, Siddon was promoted to the senior cabinet, becoming Minister of National Defence on June 25, 1993. In this role, he was responsible for ordering new EH-101 navy helicopters to replace the aging Sea King helicopters. The deal was finalized, but the opposition Liberal Party of Canada made it an election issue and argued that the helicopters were too expensive. After winning the election, the Liberals cancelled the contract and incurred cancellation fees of $500 million (CAD). The Sea Kings have since had numerous crashes and require 30 hours of maintenance for every hour of flight time. Siddon entered the 1993 election expecting a tough battle. His support for native land claims and his earlier fishing quotas had made him one of the top targets of the new Reform Party of Canada. Siddon ended up finishing third behind Raymond Chan of the Liberal Party and Nick Loenen of Reform. After federal politics Siddon returned to the private sector, but remained active in Tory politics. He supported Peter MacKay's leadership bid in 2003, and later became an early advocate of union between the Tories and Canadian Alliance. Following his federal political career, Siddon remained active as a consultant, lecturer and corporate board member. He speaks frequently on the political challenges of combating global climate change and the long range implications for water supply management. Siddon was the founding Chair of the Okanagan Water Stewardship Council, and a member of the RBC Blue Water Advisory Panel. In 2007, he was awarded a Doctorate of Laws from the University of British Columbia | Okanagan, received the University of Alberta Honour Award in 2009, the 2010 UBC Alumni Award of Distinction, and was the 2017 recipient of the University Of Toronto Engineering Alumni Hall of Distinction Award. Siddon made a return to politics when he was elected to the Board of Education in Penticton, BC in November 2008. His campaign was based on more openness by the board with fewer in-camera meetings. Siddon was also a strong vocal opponent to the board's decision to tear down a historic auditorium and gymnasium in the local high school. Following a successful three years on the School Board, in 2011 Siddon decided not to seek re-election, but rather