XV Corps
Shown here is the insignia of the XV Corps. The Y was originally given as it was formed in Egypt and designated as Y Corps. When it changed to XV Corps designation and transfered to the Western Front the insignia stuck and went with it. One of the reasons for keeping it was that with some ingenuity three Roman 'V's put together can produce a Y and three V's would be fifteen.
The Corps was commanded on the Somme by Lt-General Henry Horne, who would go on to be 1st Army commander due in someway to the success he and the Corps achieved at certain points during the Somme battles.