In 1921 a war memorial was erected in front of St. Helen's House in remembrance of the 69 old boys of the school killed during the First World War, in the shape of an obelisk. This was designed by Sir Reginald Blomfield and the cost of around £650 was raised by subscriptions from staff, boys, and the public. The memorial was unveiled on 11 November 1921 by Old Derbeian Lt. Col. C. A. Lewis and dedicated by Charles Abraham, Bishop of Derby. The names of 48 old boys of the school killed during the Second World War were added to the memorial after the end of that war.