Although WW I is now often referred to as the 1914-1918 War, if you look closely at the inscription on the base of the
cenotaph it reads 1914-19.
Although the armistice was signed on the 11th hour of the 11th day of the 11th month 1918 at which point the hostilities ceased. Peace was not official until the
Treaty of Versai was signed in June 1919 the British public then celebrated with Peace Celebrations.