A previously unknown letter from Winston Churchill has been discovered during an investigation into Edward Harrison, the World War I army chemist credited with the invention of the gas mask.
Churchill, then minister of Munitions, tells Harrison's widow that "it is in large measure to him that our troops have been given effectual protection from the German poisonous gases".
The chemist died just days before the end of the war, apparently working himself to death striving to develop the perfect gas mask for mass production.
But his work on the gas mask had already saved countless soldiers from the slow and agonising death caused by breathing poisonous gas in the trenches.
For his work he was decorated with the highest honours including France's Legion d'Honneur.
In his letter, Churchill notes that had he not died, Harrison was to be promoted to head of chemical warfare. He was buried with full military honours.