His maternal great-grandfather was Sir Watkin Williams-Wynn, 4th Baronet and his great-great grandfather was British prime minister George Grenville.

[3][4] From 1884 to 1886, Wintour served with the Royal West Kents during the Mahdist War, and was promoted to the rank of captain in 1887.

[4] Wintour, promoted to the temporary rank of brigadier general on 24 December 1914,[9] was given command of the 84th Brigade, part of the 28th Division, the very next day.

He was relieved of his command on 23 February 1915 after the brigade lost a hundred yards of trench during a raid by the Imperial German Army.

[4] Major-General Edward Bulfin, GOC 28th Division, visited Wintour's headquarters and told him that he was incapable of commanding a brigade in the field,[4] to be replaced by Brigadier General Louis Bols.

Wintour returned to the Western Front on 30 June 1915, serving as Deputy Assistant and quartermaster-general, until 9 November 1915.

[10] Photocopies of memoirs from Wintour's time in service, including an account of the Tochi Valley expedition in 1897 and a complaint relating to conditions in the trenches on the Western Front of World War I from 1915, are housed in the Liddell Hart Centre for Military Archives at King's College London.