Wikipedia:

The Ordnance BL 9.2-inch howitzer was the principal counter-battery equipment of British forces in France in World War I. It equipped a substantial number of siege batteries of the Royal Garrison Artillery. It remained in service until about the middle of World War II.
The origins of a British heavy "siege" howitzer lie in advances in technology and the 21 cm howitzers used by the German field army.[6] UK had purchased Skoda 9.45-inch howitzer from Austria in 1900 for service in South Africa. A practice camp in the 1900s showed this howitzer's high minimum elevation was a major problem. In due course Britain decided to develop its own heavy weapon, but retained the Skoda transport technique of moving it in three loads on wheeled trailers (either horse or traction towed). A trial gun was received in 1913 and fired at Woolwich and Shoeburyness during the winter. In July 1914 it was sent to the tactical firing range at Rhyader with a siege company. The assessment was "This equipment is a vast improvement on any other in use in the siege artillery, and is worth taking with an army." Major General von Donop, Master-General of the Ordance, immediately ordered 16 guns[7] and a further 16 were ordered in October 1914. The prototype gun, "Mother", was in action in France on October 31, 1914 and production guns entered service in 1915.[2]