Mallet's Mortar was a British siege mortar built for, but never used in, the Crimean War
The mortar was design by Robert Mallet. It was constructed in sections so that it could be transported.
Robert Mallet first made his design public in 1854. There was little response from the authorities until Mallet wrote to the then Prime Minister Lord Palmerston in March 1855. Palmerston was taken with the idea and instructed Board of Ordnance to arrange for the construction of two mortars of Mallet's design.
http://en.wikipedia.org/wiki/Mallet's_Mortar