Two years later he showed his gratitude to his constituents, inviting 2,000 to tea at Lyons Corner House, followed by a tour of the Palace of Westminster. He arranged for the visit to be filmed, which is now stored in the BFI National Archive. However, after the breakdown of his marriage, in spring 1933 he wrote to Neville Chamberlain to say that he would be standing down "for reasons of health." He subsequently divorced in late 1933, due to his affair with Iseult Margery Hazlehurst. His final debate was on 1 May 1935, on the subject of Pedal Cyclists. Beaumont-Thomas married his second wife Iseult in 1934, and returned to working in the family business. He got involved in an early lock or viaduct based version of the Thames Barrier, to solve flooding of the lower reaches of the River Thames. At the outbreak of war, Beaumont-Thomas signed up to be reactivated, much as though his health was graded B1. In part due to his fluency on French, he was appointed to the command of the enemy armaments intelligence branch at the Ministry of Economic Warfare, a post he held until May 1940. After serving as a general staff officer, he joined Military Intelligence, and in early 1941 attended an eight-week military politics course at Trinity College, Cambridge. Promoted to Colonel (Acting Lieutenant Colonel), he was to lead a mission proceeding to the Middle East. The height of the Battle of the Atlantic, the was scheduled to cross the Atlantic Ocean to the Caribbean, and then proceed south to Freetown, South Africa, and onwards to Lagos. Beaumont-Thomas would then travel onwards to Gibraltar. After leaving Liverpool on 28 November 1942, from the coast of the West Indies ( northwest of the Azores), on 6 December 1942, the ship was torpedoed by the , under the command of Gustav-Adolf Janssen. All hands and passengers made it to the four lifeboats, and started rowing to the Azores. The U-Boat resurfaced later that day, and after questioning the crew and passengers took the captain prisoner. That night a gale blew up, and although the U-Boat commander decided to track the lifeboats, her engine took on water and flooded the engine room, ceasing the search. Nothing further was seen or heard of the four lifeboats and their crews, and it was presumed that they lost their lives in the storm: 44 crew; 8 gunners; 11 passengers.