He was posted to the 5th Battalion, The Royal Australian Regiment, on 1st March, 1965, and 'served in South Vietnam during 1966/67 He returned with his battalion to South Vietnam in February 1969 as Platoon Sergeant 10 Platoon D Company.
In May 1969, while following up an enemy force the platoon commander and two soldiers were seriously wounded by booby traps. The platoon had suffered heavy mine casualties in March 1969 and Sergeant London, realising the concern of his troops at finding themselves again in an extensively booby trapped area took immediate and firm control. At great personal risk, which showed outstanding courage and leadership Sergeant London moved around the area to clear booby traps and organise the dangerous helicopter evacuation of the wounded. He then led his men safely out of the area, locating and delousing several more booby traps, to continue an aggressive pursuit of the enemy.
In June, 1969, an enemy battalion occupied the village of Binh Ba. Sergeant London commanded 10 Platoon, whose total strength at this time was fifteen men. In two days of continuous action, 10 Platoon assaulted the enemy entrenched in houses and bunkers. Fierce close quarter fighting took place as 10 Platoon attacked enemy in house after house. On at least six occasions, the platoon was held up by enemy rocket and machine gun fire, Sergeant London, without regard for his own safety, directed and personally led assaults into the houses, throwing grenades at enemy firing from windows and from behind walls. In one house, he shot two enemy dead at point blank range.
His continuous bravery and leadership were a source of great inspiration to his men and resulted in his platoon killing over twenty enemy during the battle. His exemplary conduct against the enemy throughout 1969 reflects great credit on himself and The Royal Australian Regiment.