On the outbreak of World War I, and now married, he was promoted to Lieutenant. Posted to the 14th Brigade, he served in the trenches. Promoted to Captain, for three years from August 1915 to August 1918, Beaumont-Thomas was adjutant to the 14th Brigade of the Royal Horse Artillery. He served in the Battle of the Somme in July 1916, where the division in which he served held ground around the village of Mametz. In January 1917, he was awarded the Military Cross for holding a stretch of ground after two of his companions had been killed.
Inter-war period
Promoted in June 1918, to Major in charge of the 76th Battery, Royal Field Artillery, he was tempted to stay on, but decided in light of the death of his father to rejoin the family business, Richard Thomas & Co Ltd. Rather than taking a board position, he took a working post to learn the business. He did however retain his military commission, appointed to command a Battery in the 83rd Welsh Brigade, the Territorial Army in Cardiff. After resigning his commission in 1923, as well as his duties as Deputy Chairman of Richard Thomas & Co Ltd, he was a Justice of the Peace and a Conservative County Councillor in Herefordshire. In 1923, he stood unsuccessfully in Llanelli, and in 1924 again unsuccessfully for Pontypool.
Beaumont-Thomas was adopted as the Prospective Parliamentary Candidate for Birmingham King's Norton in 1925. He received great support from the ousted Conservative candidate of 1927, the car manufacturer and industrialist Herbert Austin, including the placement of posters in within his Longbridgecar factory which was located within the constituency. Beaumont-Thomas was elected to the seat of Birmingham King's Norton in 1929, ousting Labour'sRobert Dennison. He took part in his first debate on 24 March 1930, on disarmament. 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.
World War II
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, 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, 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. After being assumed dead the following year, his name was inscribed on the Brookwood Memorial, together with 3,500 other men and women of the land forces of the Commonwealth who died in action during the Second World War and have no known grave. His family later learnt that Beaumont-Thomas was en route to brief forces with regards the Battle of Crete, to recapture it from the Nazis. His enjoyment in being involved in such a mission was that at the time of his departure, his son Nigel was a Prisoner of War in Italy. Released as the allies undertook the Italian Campaign, Nigel Beaumont-Thomas was second in command of the 4th Parachute Squadron within the 1st Airborne Division, when they parachuted into Arnhem as part of Operation Market Garden, where he was killed in action.
Personal life
On his tour he met Pauline Grace Marriott, the daughter of Sidney Frederick Marriott the Governor's Commissioner for Colo West, Fiji. A relationship disapproved of by his mother, the couple married in a Register office with the bride's mother was a witness. On visiting his mother, the couple told her of their marriage, and she insisted on them remarrying in a church, which they later did at Holy Trinity, Brompton. The couple lived at Great Brampton House, in Madley, Herefordshire, and had four children: Richard Lionel, Nigel, Paul and Pearl. An affair with Welsh seamstress Nancy Turner daughter of Arthur Turner of Cardiff, bore him a son, Noel David Jeffries Turner. After he started a prolonged affair with Isuelt Marjery Bland daughter of Oscar Theodore Bland of Riversdale, Insinga, Rhodesia, at the time wife of Henry Edward Hazlehurst, Pauline divorced him in 1933. He married Iseult Hazlehurst on 5 January 1934 in Kensington, London.
