Mosley was born in Staffordshire in 1848 the eldest son of Sir Tonman Mosley, 3rd Baronet, of Ancoats (9 July 1813 – 28 April 1890), who succeeded to the title of 3rd Baronet Mosley, of Ancoats, on 24 May 1871, and wife Catherine Wood (died 22 April 1891), daughter of The Reverend John Wood of Swanwick, Derbyshire and Emily Susanna Bellairs (daughter of Abel Walford Bellairs and Susannah Lowley).
Eton College.
Mosley"s family were Anglo-Irish. His branch were prosperous landowners in Staffordshire. He was educated at Eton, and went on to own around 3,800 acres (15 km2) of land.
His residences included Rolleston Hall in Rolleston on Dove and he was engaged in farming and cattle breeding.
He succeeded the baronetcy on 28 April 1890. Mosley was nicknamed "Baronet John Bulletin" due to his resemblance to John Bulletin, the national personification of Great Britain.
Caricature.
