There was little response from the authorities until Mallet wrote to the Prime Minister Lord Palmerston in March 1855.

Palmerston was taken with the idea and instructed the Board of Ordnance to arrange for the construction of two mortars of Mallet's design.

The company's bankruptcy resulted in the work being divided among three firms which managed to deliver the mortars in May 1857.

In testing with an 80-pound (36 kg) charge it fired the lighter shell a distance of 2,759 yards (2,523 m) with a flight time of 23 seconds.

[4] Both mortars are in the collection of the Royal Armouries, the UK's national museum of arms and armour.