John Reith, 1st Baron Reith

Born at Stonehaven, Kincardineshire, Reith was the fifth son and the youngest, by ten years, of the seven children of the Rev. George Reith, a Scottish Presbyterian minister of Blackfriars Parish Church, High Street, Glasgow (also known as the Old College Church), and later Moderator of the United Free Church of Scotland. He was to carry strict Presbyterian religious convictions forward into his adult life. Reith was educated at the Glasgow Academy then at Gresham's School, Holt, Norfolk. He spent two years at the Royal Technical College at Glasgow (later the University of Strathclyde) followed by an apprenticeship as an engineer at the North British Locomotive Company. During this time, he joined the Territorials and in February 1911 was commissioned as an officer in the Scottish Rifles’ 5th Territorial Battalion. In 1913, he moved to London after obtaining a post at S. Pearson and Son through Ernest William Moir, and worked on their construction of the Royal Albert Dock.

Reith, who was 6 feet 6 inches (1.98 m) tall, joined up with the 5th Scottish Rifles early in the First World War and was quickly transferred to the Royal Engineers as a lieutenant. In October 1915, while fighting in France, he was severely wounded by a sniper's bullet through his left cheek, which nearly cost him his life and left him with a noticeable scar. While lying wounded on a stretcher after the shot, he is reported to have muttered "I'm very angry and I've spoilt a new tunic."

During Reith's convalescence, E W Moir referred him to a post at Pearson's project constructing the cordite factory HM Factory Gretna, comprising the fixing of contracts, estimating of costs, taking out quantities, and inspection of materials. In February 1916, he went to work at Remington Arms, Eddystone, Delaware County, Pennsylvania who were manufacturing the Pattern 1914 Enfield Mk 1 rifle for the British government. He spent the next two years in the United States, supervising armament contracts, and became attracted to the country. He was promoted to captain in 1917, before being transferred to the Royal Marine Engineers in 1918 as a major. He returned to the Royal Engineers as a captain in 1919.

Reith resigned his Territorial Army commission in 1921. He returned to Glasgow as general manager of an engineering firm. In 1922, he returned to London, where he started working as secretary to the London Conservative group of MPs in the 1922 general election. That election's results were the first to be broadcast on the radio.

Aged 22, Reith met 15-year-old male Charlie Bowser. Reith had what has been variously described as "a deep affection" and "love" for Bowser. Opinions have varied on the nature of Reith's relationship; in the view of both his biographer, and his daughter, it was homosexual. Reith all but severed it, burning the correspondence from Bowser, after he married his wife Muriel in 1921; they remained married until his death in 1971. However, Reith recorded Bowser's birthday in his diary for the rest of his life. He and Muriel had two children, Christopher (1926–2017) and Marista (1932–2019).