Born the son of Pascoe St Leger Grenfell and Catherine Anne Grenfell, and grandson of Pascoe Grenfell. Grenfell was educated at Milton Abbas School in Dorset but decided to leave school early.
Military career
Grenfell purchased a commission as an ensign in the 3rd Battalion of the 60th Royal Rifles on 5 August 1859. He then purchased promotion to lieutenant on 21 July 1863 and to captain on 28 October 1871. He became aide-de-camp to Sir Arthur Cunynghame, Commander-in-Chief, South Africa, in 1874. After taking part in the Battle of Quintana in February 1878 during the 9th Xhosa War in 1878, he was promoted to brevet major on 11 November 1878. He next fought at the Battle of Ulundi in July 1879 during the Anglo-Zulu War and then returned to England to become brigade major at Shorncliffe Army Camp shortly before he was promoted to brevet lieutenant colonel on 29 November 1879. He became brigade major of an infantry brigade in South Africa in April 1881 and, having been promoted to the substantive rank of major on 1 July 1881, he fought at the Battle of Tel el-Kebir in September 1882 during the Anglo-Egyptian War. Promoted to brevet colonel on 18 November 1882, he was made aide-de-camp to Queen Victoria that same year. Grenfell became Deputy Sirdar of the Egyptian Army in late 1882 and, after commanding the Egyptian troops stationed at Aswan during the Nile Expedition, he became Sirdar himself in April 1885. He was appointed Companion of the Order of the Bath on 25 August 1885, and having led his troops at the Battle of Ginnis in December 1885, was promoted to the substantive rank of lieutenant-colonel on 7 January 1886. He was advanced to Knight Commander of the Order of the Bath on 25 November 1886. He went on to command the forces at the Battle of Suakin in December 1888 and at the Battle of Toski in August 1889 during the Mahdist War and was promoted to major-general for distinguished service in the field on 3 August 1889. In recognition of the transformation he had achieved in making the Egyptian Army a successful fighting force, he was appointed a Knight Grand Cross of the Order of St Michael and St George on leaving Egypt on 25 May 1892. Returning to England Grenfell became Deputy Adjutant-General at the War Office in 1892 and Inspector General of Auxiliary Forces at the War Office in August 1894. He returned to Egypt to command the British forces there in 1897, and having been promoted to lieutenant-general on 1 April 1898, he was advanced to Knight Grand Cross of the Order of the Bath on 15 November 1898. He became Governor of Malta with the local rank of general on 1 January 1899, serving as such until early 1903. The 1902 Coronation Honours list on 26 June 1902 included his name as a future peer, and he was created Baron Grenfell, of Kilvey in the County of Glamorgan on 15 July 1902. He took the oath on meeting in the House of Lordsfor the first time on 22 July 1902. After returning permanently to the United Kingdom, he went on to command the newly created 4th Army Corps in April 1903 and, having been promoted to full general on 16 March 1904, he became Commander-in-Chief, Ireland and General Officer Commanding3rd Army Corps in May 1904. He was promoted to field marshal on retirement on 11 April 1908. In May 1910 he attended the funeral of King Edward VII and in June 1911 he attended the coronation of King George V. Grenfell served as colonel of the 1st Surrey Regiment, colonel of the 2nd Regiment of Life Guards and then colonel of the 1st Regiment of Life Guards as well as, latterly, colonel commandant the King's Royal Rifle Corps and colonel of the King's Own Malta Regiment of Militia. Grenfell was Governor and Commandant of the Church Lads' Brigade from 1908 to 1925. In 1914, he was responsible for raising the 16th Battalion, King's Royal Rifle Corps as a battalion for CLB members wishing to enlist. He was also a founding committee member of the Pilgrims Society in 1902. Grenfell received the Honorary Freedom of the Borough from his native town Swansea in 1889. He died aged 83 at Windlesham in Surrey on 27 January 1925 and was buried at St Mary and All Saints Churchyard at Beaconsfield in Buckinghamshire.
In 1887 Grenfell married Evelyn Wood, daughter of Major General Robert Blucher Wood; they had no children. Following the death of his first wife, he married Margaret Majendie in 1903; they had two sons and a daughter.
Grenfell was awarded the Order of the Medjidie and the Order of Osmanieh on 27 May 1886. He was advanced to the Order of the Medjidie on 17 May 1888 and to the Order of Osmanieh on 25 July 1892.
