An officer with the Royal Army Medical Corps during the First World War, he was posthumously awarded the Victoria Cross for his actions in late July–early August 1917, during the Battle of Passchendaele.

[2] He completed his Bachelor of Arts degree in 1899, before he did some travelling and then spent one year in the research group of Gowland Hopkins[3] before continuing his medical studies at Guy's Hospital, London.

[3] When the First World War began in 1914 Ackroyd was nearly 37 but, despite his age, occupation and being married with three small children, he joined up and on 15 February 1915 was commissioned a Temporary Lieutenant in the Royal Army Medical Corps (RAMC).

In July 1915, Ackroyd was sent to France, where he was attached as a medical officer to the 6th Battalion of the Royal Berkshire Regiment, (Princess Charlotte of Wales's), part of the 53rd Brigade, 18th (Eastern) Division.

[1][3] Of the opinion that he had recovered Ackroyd by September was asking the Army Medical Board to allow him to return to his regiment in France, which he accomplished in December 1916.

His heroism was the means of saving many lives, and provided a magnificent example of courage, cheerfulness, and determination to the fighting men in whose midst he was carrying out his splendid work.

[6]Ackroyd was subsequently killed on 11 August 1917 in Jargon Trench on the western edge of Glencorse Wood, Ypres, Belgium by a sniper.

[3] His second in command Private Albert Scriven wrote to Ackroyd's widow describing what happened: “I was acting orderly corporal and on hearing the news I took a party of stretcher bearers but on arrival found he was dead.

"[7][8] His Victoria Cross (number 851) was presented by King George V at Buckingham Palace to his widow Mabel and son Stephen on 26 September 1917.

[7] The proceeds from the sale were used to endow an annual medical scholarship at Gonville and Caius College, Cambridge, Harold Ackroyd's alma mater.