Returning to Scotland he graduated LLB at the University of Edinburgh in 1937, and served his apprenticeship as a Writer to the Signet with Shepherd and Wedderburn, but soon found his preferred field as an advocate.
When World War II broke out Robertson joined the 8th Battalion The Royal Scots, serving first as a weapons instructor.
He was later commissioned and as captain and intelligence officer for the 44th Lowland Brigade (15th Scottish Division), he distinguished himself in Normandy and NW Europe and the campaign from D-Day to the end of the war, being mentioned in dispatches.
Robertson presided over the 1974 case of Jessie McTavish, a Glasgow nurse accused of the murder of one of her patients and the assault of four others.
His brother was James Wilson Robertson, the last British Governor-General of Nigeria, while his daughter Sally married businessman Nick Kuenssberg.