Casement, Thomas Hugh (‘Tom’) (1862/3–1939), soldier and adventurer, is believed to have been born aboard a ship bound for Boulogne (where his birth was registered on 3 January 1863), third child and second son among one daughter and three sons of Roger Casement (1819–77), a retired army officer, and his wife Anne (née Jephson) (1834–73). Sir Roger Casement (qv) was his younger brother. His father was a colourful character who served with the 3rd Light Dragoons in India, seeing action in the 1842 Afghan campaign and the first Anglo–Sikh war (1845–6). After selling his commission in 1848, he travelled to Hungary to aid Kossuth's struggle against Austria, during which time he was reputed to have carried a message from Kossuth to Lord Palmerston in London. Though he rejoined the army in the year of his marriage (1855) as a captain in the North Antrim Rifles, he resigned owing to ill health in 1858. Thereafter the family seem to have travelled frequently in Europe, resided for a time in the Isle of Man and the Channel Islands, and lived, probably in difficult financial circumstances, at a series of addresses in suburban and outer London. Capt. Casement was from a protestant background, while his wife was Roman catholic; on 5 August 1868 she had her three sons baptised in secret by a Fr Poole at the catholic parish church in Rhyl, north Wales. After her death in 1873, the four children were sent to Magherintemple House, near Ballycastle, Co. Antrim, to live with their father's family. Capt. Casement played little role in the life of his children after this and died in mysterious circumstances in Ballymena in 1877.
The Casement children were made wards in chancery of their uncle John of Magherintemple House, and Tom Casement became an apprentice in the mercantile marine at an early age (possibly 13). After some years at sea he travelled to Australia and New Zealand, where he prospected for gold. In about 1895 Casement moved to South Africa, where he later served with distinction in the British army during the Boer war. His time in the army afforded him the opportunity to meet many worthies including Lord Roberts (qv) and Jan Smuts. After the war he was appointed mines commissioner at Barberton, near Johannesburg, and it is said that he later became a commissioner for native affairs. Despite this career Casement was a lifelong drain on the finances of his beloved brother Roger, and tried his hand at a host of unsuccessful business ventures including farming, mining, and inn-keeping. During the first world war he fought under Smuts in German East Africa and returned to Ireland on its cessation.
Smuts began to take an interest in the Irish question during the war and had been in correspondence with Casement about the issue since 1914. In June 1920, while Casement was working on the construction of a bank in Tralee, Éamon de Valera (qv) contacted him with a request to arrange a meeting with Smuts. Casement wrote to Smuts from Castle Ffrench, Galway, on 30 May 1921, suggesting that the two men meet in London before the imperial conference due to take place the following month. In the course of his letter, he wrote: ‘I won't worry you until I feel that you have a few minutes to give an old friend and comrade and one who has stood to you through all kinds of weather . . . Privately I have always felt that you would some day be a big factor in settling our question.’ On 30 June 1921 Casement introduced Smuts's private secretary, Capt. Lane, to de Valera and had talks with Alfred Cope (qv), during which he successfully counselled the release of many of the Sinn Fein leaders. On 5 July the de Valera / Smuts meeting took place and helped to pave the way for the signing of the truce on 11 July 1921.
After independence, Casement helped to found the Coast Guard Life Saving Service of the Irish Free State under the auspices of his friend C. H. Gordon Campbell (qv) and the Department of Industry and Commerce. A well known and much liked character in Dublin, Casement is the sole inspiration for the character George in the play by Denis Johnston (qv), ‘The moon in the yellow river’ (1931). So pleased was Casement, it is said, that he sat applauding Arthur Shields (qv), who played George, every night the play ran. Retiring without a pension from the Coast Guard Life Saving Service in 1933, he successfully sued London Express Newspapers for £500 damages in a libel action for an article that appeared in the Daily Express on 22 October 1932. Despite this windfall, Casement spent his remaining years in straitened circumstances owing to his highly generous and quixotic nature. Fanatically fond of rugby, he was a member of the Rand Club while in Southern Africa. He was an active member of the Arts Club, Dublin from 1920. He was given to threatening suicide in later life: his body was recovered from the Grand Canal, near Baggot St. bridge, Dublin, clad in pyjamas and dressing gown, on 6 March 1939.
His first marriage, to Blanche Balharry, ended in divorce c.1911; the second marriage, to Katje Ackermann, artist and businesswoman, ended in separation.