When Lord Chelmsford left his base camp at Isandlwana to reinforce the mounted patrols he had sent out the previous day, he left behind a large widely spread camp at the base of the mountain. By midday of 22nd January, the right flank of the defending British had been overwhelmed and the Zulu hordes were in the camp, stabbing and clubbing the disorganised and terrified soldiers.

Private Wassall was one of the Imperial Mounted Infantry (Carrington's Horse), who had been left in the main camp by Chelmsford. Having no particular duty, he and his fellow Mounted Infantrymen were stood down and in camp when the Zulus struck. As the right flank gave way, it became 'every man for himself'. Wassell, in shirtsleeves and weaponless, hauled himself on to a small Basuto pony and joined the ranks of those trying to escape over the narrow pass on to the safety of Helpmekaar via Rorke's Drift. Only a few were able to reach safety by this route before the Zulu right horn had reached this escape route and had advanced around the mountain to cut off all retreat. There was no alternative but to head off across rough country and face swimming the Buffalo River.

With the Zulus in close pursuit and the steep hills on either side, the escapees had little option but to follow a hazardous four mile route that led them to a spot now called Fugitives' Drift, where there was a ford. All along the route, men were dying as the Zulus overtook them but a number of mounted men did reach the river, including Private Wassall. What he found was a river in full spate and, in normal circumstances, unthinkable to attempt to cross. With Zulus opening fire and closing fast, Wassall urged his pony into the torrent. About halfway across he heard a cry and saw Private Westwood of his regiment being swept round in a raging whirlpool. Despite the approaching Zulus, Wassall turned his mount and headed back to the bank, he coolly tied his horse to a bush and waded in after Westwood. Reaching him Wassall dragged the half-drowned man to the bank and hauled him onto his pony. Then, pursued by a hail of bullets and spears, pony and men plunged into the river and managed to reach the far bank, scramble up the steep sides of the gorge and stagger on to Helpmekaar. The next day, he was back in the saddle and was one of the force that relieved the defenders at Rorke's Drift.

At the time he received his Victoria Cross at Pietermaritzberg a few weeks later, he was, at the age of 23, the youngest recipient. After he left the Army, he married, raised a family and lived out his life in Barrow-in-Furness until his death in 1927. He was the only survivor of Isandlwana to be awarded a VC.