[1] Born on 29 December 1873 at Fryers House, near Beaumaris, Anglesey, he was the only son of Sir Oswald Mosley, 4th Baronet, of Rolleston Hall, Rolleston-on-Dove, Staffordshire, and Elizabeth Constance, Lady Mosley (née White), daughter of Sir William White.

[1][2] He gained the rank of Captain in the 1/1st Derbyshire Yeomanry and served in Egypt during the First World War until invalided in 1916.

[7] His will was proven by probate at the Derby District Registry; his estate valued at £5000, which he left to his ageing mother and sister.

On 12 December 1895, Mosley married Katharine Maud Edwards-Heathcote (1873–1948), the daughter of Capt.

She belonged to the wealthy Staffordshire Heathcote family, who held significant property around Newcastle-under-Lyme and Stoke-on-Trent.