Harold Jacks was the son of South Shields solicitor, Robert Jacks, and his wife, Mary.

Harold attended the High School from 1899 to 1904, leaving at the age of 12 to attend Worksop College.

He trained and qualified as a solicitor, and started with his father's practice in 1913.

Harold joined the 7th Battalion, Durham Light Infantry, and served in France from April, 1915, as an Assistant Military Landing Officer.

He was severely innjured in the foot at the Battle of Ypres, 28-Apr-1915 and, once recovered, was appointed Adjutant and Captain the 3rd/7th Battalion of the Durham Light Infantry.

After this he was attached to the Headquarters Staff, Northern Command, and in November, 1916, was appointed Staff Captain to the 208th Infantry Brigade, Doncaster.

In around June 1918 he was posted oversea to the 4th Nigeria Regiment, and later on the staff of the West African Frontier Force.

He died of septicaemia in Lagos, Nigera, on 27-Jan-1919, and is buried in the Ikoyi Cemetery in Lagos.