In 1900 as managing director of Dunlop's Midlands subsidiary Clipper Tyre Company he gained prominence in the motor industry by driving a 6 hp Daimler car through England's Thousand Miles Trial with marked success.

During 1905 Wolseley—which then dominated the UK car market—purchased the goodwill and patent rights of his Siddeley Autocar Company business[4] and appointed Siddeley London sales manager of Herbert Austin's The Wolseley Tool and Motor Car Company Limited owned by Vickers, Sons and Maxim.

During World War I it grew rapidly producing aircraft engines and airframes with the assistance of distinguished staff from the Royal Aircraft Factory at Farnborough as well as motor vehicles including ambulances[1] using Rover chassis and Daimler and Aster engines and employed around 5,000 workers.

[5] He was appointed a Commander of the Order of the British Empire in the 1918 New Year Honours for his industrial services during the war.

Siddeley's new holding company established Sir W G Armstrong Whitworth Aircraft in July 1920.

To commemorate the coronation of King George VI and Queen Elizabeth in 1937, Lord Kenilworth also made a gift of £100,000 to Fairbridge Farm Schools, a charity to offer opportunities and education abroad to young people from broken homes.

[2] After his retirement he moved to Jersey where he died a few days after his wife in November 1953, aged 87, a voluntary tax exile and a rich man.