He returned to the UK and in 1965 was posted to NATO as Deputy Chief of Staff in charge of Plans, Operations and Intelligence, Headquarters, Allied Forces Central Europe in Paris where his job was to plan and execute the headquarters' move out of France. He accomplished this complex task on time and very efficiently. Promoted and knighted in 1968 he was appointed General Officer Commanding in Chief of Northern Command in the UK from 1967. Finally in 1969 he was promoted to General and appointed NATO's Commander in Chief Allied Forces Northern Europe with headquarters in Oslo. This covered German Jutland, Denmark and Norway but had no direct command responsibilities in peacetime. Walker saw his role as publicising the threat. The region faced an overwhelming and expanding Soviet force and while he did not expect Soviet direct attack he did see a strategic threat of expanding influence aimed at neutralising the Nordic countries (and possibly beyond) and clearing the path into the North Atlantic. Pointing this out did not endear him to some politicians and even his NATO superior. He retired from the army in 1972. Walker was Colonel of 7th (Duke of Edinburgh's Own) Gurkha Rifles from 1964 to 1975.