8th (City of London) Battalion, The London Regiment (Post Office Rifles), was formed on 1 April 1908 by the amalgamation of regiments under the Territorial and Reserve Forces Act 1907. Their Wikipedia page gives details about the origins of the battalion, their battle honours and how it was amalgamated with the 7th (City of London) Battalion, The London Regiment in 1921, forming the 7th London Regiment (Post Office Rifles).
It is shown as the 8th Battalion (Post Office Rifles) on the London Troops War Memorial in Threadneedle Street, London, EC2.
The Postal Museum in London also features an article on their website about the Post Office Rifles.
Credit for this entry to: Andrew Behan