[2] Born to Mary Mount Carmel Alles, a Colombo Chetty,[3] and Dr. Philip Marian Muttukumaru, a Jaffna Tamil, he and his siblings were brought up by their mother after the early death of their father.

[4] Following the war, Muttukumaru worked once again as a lawyer representing the Attorney General, in a variety of cases but soon gave up law to function as Officer in Charge, Administration in the Ceylon Defence Force Headquarters, where he assisted in the initial plans for the formation of a new Ceylon Army, including the drafting of the Army Act.

During this time he attended the Senior Officers' School, where he was taught by Field Marshal Montgomery and befriended future Israeli Defence Minister, Brigadier Moshe Dayan.

He led the Ceylon contingent of soldiers to London on ceremonial duties for the funeral of George VI in 1952, and for the Queen's coronation.

During his time as commander, the army grew in size and was deployed on several occasions to curb civil unrest and riots.

He elevated the Army Recruit Training Depot at Diyatalawa to the Army Training Centre, raised a new infantry battalion, Ceylon Sinha Regiment, promoted all commanding officer to the rank of lieutenant colonel after elevating all regular units to regimental strength; established the Headquarters of the Ceylon Volunteer Force and initiated the concept of regional commands.

In 1959, he decided to retire so that younger officers could have their chance to command, even though Prime Minister Solomon Bandaranaike asked him to stay on.

During his service in the Ceylon Defence Force, he received the King George V Silver Jubilee Medal in 1935, appointed an officer of the Order of the British Empire (Military Division) in the 1946 Birthday Honours and awarded the Efficiency Decoration.