Robertson was 38 years old, and a lance-corporal in the 10th (Service) Battalion, Royal Fusiliers (Stockbrokers),[1] British Army during the First World War when the following deed took place for which he was awarded the VC.

Robertson sent back two men to get reinforcements, and remained at his post (with only one other man), firing his Lewis gun and killing large numbers of the enemy, who were in range on his right.

No reinforcements came up, and, realising that he was being completely cut off, he withdrew with the only other survivor of the garrison of the post, to a point about ten yards further back where he successfully held his position.

The position was, however, made impossible for him by the heavy hostile bombing and machine-gun fire, so he was forced to again withdraw and arrived at a defended post.

Robertson was alone throughout these operations, except for the presence of one other man who later was killed, and the most determined resistance and fine fight which he put up undoubtedly prevented the enemy from making a more rapid advance.