In 1959, 99th Brigade was sent to Singapore in advance of the forthcoming elections. Walker was told to take charge of internal security throughout Singapore Island. The 99th Brigade were highly skilled jungle fighters, but urban Singapore was a very different environment, and internal security an entirely new assignment. Walker immediately instituted a typically thorough training programme. No manual existed on the subject, so Walker wrote one. "Internal Security in a City" became the army standard on the subject. The elections passed peacefully. Walker relinquished command and attended the Imperial Defence College in London. He was unimpressed by the politically tuned officers and considered that politics was the business of politicians not soldiers. After the course, in 1961, he was promoted to Major General and appointed General Officer Commanding 17th Gurkha Division and Major General, Brigade of Gurkhas. 17 Division was the operational headquarters for all non-Malayan formations (99 Gurkha Infantry Brigade and 28 Commonwealth Brigade) and divisional units in Malaya.