From the outbreak of the First World war up until 1920, Horace had been director of the uniform and equipment department of the British Red Cross and Joint War Committee. The book The British Red Cross in Action by Beryl Oliver records that because of the immense scope of work being faced by the Red Cross Society at the outbreak of war, committee work was decentralised into departments. Horace took charge of the Medical Comforts to Home Hospitals. He also served on the Fire Survey Force for Prevention of Fires in Red Cross Hospitals.

In 1916, Horace is recorded as having sailed aboard Nyanza on 19 April from London to Malta in connection with Red Cross business.

Through his position with the Auctioneers and Estate Agents Institute, he was involved in the purchase of the former Star & Garter Hotel on behalf of the British Red Cross Society. The deeds were handed over by the institute in 1915 and a new purpose built home was constructed from funds raised by the British Women's Hospital Committee. It was eventually opened by King George V and Queen Mary in 1924.

For his war work, Horace was appointed on 1 January 1918 to be a Commander of the Most Excellent Order of the British Empire, which had been instituted the previous year to recognise wartime work by civilians. Horace received the award in the capacity of Head of Equipment Services, Headquarters Staff, British Red Cross Society.