In February 1810, the Peninsular war was not going well. France controlled most of Spain and the Spanish government had retreated to the port city of Cadiz. In an effort to complete their surrender, the French forces under Marshalls Soult and Victor besieged the city with 70,000 men. Inside the city at the time were 2,000 Spanish troops. Attempts were made, without success, to lift the siege in October 1810 and again the following year. The siege lasted for over 2 years but did not succeed as the Fench were unable to block off the sea route and the allied forces of Spain, Britain and Portugal were able to supply and reinforce the city by sea. In July 1812 with Wellington’s victory at Salamanca and subsequent capture of Madrid, Marshall Sault realised he was in grave danger of being cut off from the rest of the French army in Spain. He ordered a retreat from Cadiz, leaven behind a number of siege guns.
One of these guns was presented by the Spanish Government to the British Naval Commander with a request that it be presented to the Prince Regent and set up as a memorial to the Victory at Salamanca and the lifting of the siege. It arrived in London and went on public display in August 1816. It was an impressive and terrifying piece of sculpture, although reports at the time described it as an ineffective weapon, inaccurate in firing and causing very few casualties during the siege.
The inscription reads:
To commemorate the Raising of the Siege of Cadiz, in consequence of the Glorious Victory obtained by the Duke of Wellington over the French at Salamanca, on the 22d July 1812: This Mortar, cast for the destruction of that Great Port, with Powers surpassing all others, and abandoned by the Besiegers on their Retreat, was presented as a token of respect and gratitude by the Spanish Nation, To his Royal Highness the Prince Regent.
It can be seen today on Horse Guards Parade.