Sunday, 8 May 2016

Mallet's Mortar - Fort Nelson

Post from our roving correspondent 'Mr Steve'.

Last year I went to Fort Nelson which is located in the hills just north of Portsmouth and where the Royal Artillery has its Museum. Originally built as one of Lord Palmerston’s 19th C follies it now houses a fine collection of artillery from through-out the ages.

As I only took photos of those things that interested me I cannot give you a full guided tour so I will just pick out some of the more interesting items and occasionally drip them in from time to time. This short article therefore is about the giant mortar which stands outside the fort.

It was 1854 and the British government wanted a big mortar however it also needed to be easily transported (i.e. an IKEA version) so they put out a requirement for tender and given that they were in the middle of the Crimean war they wanted it urgently.

One of the people who submitted plans was Robert Mallet, the son of an Irish iron foundry owner; he had graduated in Science and Mathematics and was also extremely interested in earthquakes and their energy waves. His proposal was that if you threw up a big enough bomb then it didn’t have to actually hit its target to do really serious damage. Using his iron manufacturer skills he submitted a plan for a giant mortar made up from multiple parts and which would sit on three layers of heavy bulk timber rather than on a purpose built base.

Henry John Temple, 3rd Viscount Palmerston,
Prime Minister, 1855-58 and 1859-65 
Initially meeting with no interest his idea was picked up by Palmerston himself and he instructed that two of Mallet’s mortars should be built however by the time they were ready for trialling the war they were designed for had been over by at least a year.

Unlike other follies these were actually fired, a grand total of nineteen rounds with each shot causing various amounts of damage to the first mortar and with no prospect of curing the faults the project was cancelled.

Claimed by many websites as the largest mortar ever made, each shot weighed over a ton and had a range of around a mile and a half.

(However according to Wikipedia:The largest mortars ever developed were the Belgian "Monster Mortar" 36 French inches; 975 mm;  1832, Mallet's Mortar 36 inches; 910 mm; 1857 and the "Little David" 36 inches; 914.4 mm; developed in the United States for use in WW2.All three mortars had a calibre of 36 "inches", but only the "Monster Mortar" saw action ) and it also depends on how you classify the seven WW2 German Karl Mortars.

The unfired gun is the one in the picture whilst the test gun is also still in existence and is currently at the army base at Woolwich.

Mallet went back to his study of earthquakes; something for which he was clearly much more suited to because he would later became very highly respected for his work on seismology.

There are much better photos easily available on line and which show the shear scale of this thing much better than my long distance picture does, I do think that you might need a mate to help you with lifting up one of the balls for loading.

The link below is just one of the better articles on this weapon (and is also nice and short)


  1. That is one seriously BIG piece of kit. When you think that several men could get inside the bore and not be visible, you realise just how huge it is. The one at Woolwich is very impressive too, even if it was a bit "broken".


    1. For its time that was probably one of the most advanced guns on the planet and the fact that they had problems getting the thing to stand up to the tremendous stresses the firing caused shows how on the edge of technology they were.

      The German Karl mortars and later railway guns aren't really a fair comparison as the technology in the early to mid 20th century had moved on considerably.

      I went to Woolwich years ago, my memories are of French guns captured at Waterloo and some amazing Indian artillery pieces captured over several different periods in the 19th century.

  2. Excellent post, I grew up just down the hill from Fort Nelson and always used to love going there. Another one of the forts (Fort Brockhurst) used to put on some great American civil war displays!

  3. I strongly suggest that when visiting this museum then for one of your party "today's their birthday", This greatly increases your chance of firing the midday gun (a 25 pdr).

    As promised I will be sending in more pictures throughout the next few months of more pieces that caught my eye during my visit.