On 26 September 1914, he was commissioned a second lieutenant in the Royal Field Artillery Territorial Force (2nd East Anglian Brigade).

[5] He served in France with the Royal Artillery, was mentioned in dispatches twice and as a major, was appointed to the Distinguished Service Order (DSO) in 1918.

Lawrence served in this capacity until, in 1932, he was appointed as a judge of the King's Bench Division, receiving the customary knighthood.

He was chosen as an experienced judge to be the lead to Norman Birkett in the British delegation to the Judicial group in the Nuremberg trials, though not (as some thought) arising out of his friendship with Attlee who was by then Prime Minister.

His conduct of the trials was praised by many of those involved who appreciated his striving to understand the relevance of each piece of evidence, and willingness to stop long-winded counsel.

Lawrence was not considered an exceptional legal talent but won acclaim for delivering a very clear judgment (largely penned by Birkett) that expressed the moral sense of the Court's conclusions.

Their son John was a well known amateur jockey and horse racing journalist; he too only used the title Lord Oaksey.