HMS M3, built by Armstrong Whitworth

Armstrong Whitworth

Sir W G Armstrong Whitworth & Co Ltd was a major British manufacturing company of the early years of the 20th century. Headquartered in Elswick, Newcastle upon Tyne, Armstrong Whitworth engaged in the construction of armaments, ships, locomotives, automobiles, and aircraft.-History:In 1847,...

, Newcastle Upon Tyne

Newcastle upon Tyne

Newcastle upon Tyne is a city and metropolitan borough of Tyne and Wear, in North East England. Historically a part of Northumberland, it is situated on the north bank of the River Tyne...

 was an M class submarine

British M class submarine

The British Royal Navy M-class submarines were a small class of diesel electric submarine built during World War I. The unique feature of the class was a 12-inch gun mounted in a turret forward of the conning tower.-Background:...

 of the Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

.

M3 was ordered from Armstrong Whitworth

Armstrong Whitworth

Sir W G Armstrong Whitworth & Co Ltd was a major British manufacturing company of the early years of the 20th century. Headquartered in Elswick, Newcastle upon Tyne, Armstrong Whitworth engaged in the construction of armaments, ships, locomotives, automobiles, and aircraft.-History:In 1847,...

 on 28 July 1916 and laid down at Elswick

Elswick, Tyne and Wear

Elswick is a ward of the city of Newcastle upon Tyne, England, in the western part of the city, bordering the river Tyne. One of the earliest references to the coal mining industry of the north east occurs in 1330, when it was recorded that the Prior of Tynemouth let a colliery, called Heygrove, at...

 in December as an M-class submarine, but was referred to as K20. She was launched on 19 October 1919, and commissioned as M3 on 16 March 1920. After completion of trials on 17 August, she was placed in reserve.

Service

M3 was recommissioned on 4 July 1921 under the command of Lieutenant-Commander Hugh Marrack

Hugh Marrack

Rear Admiral Hugh Marrack, DSC, CBE, was a submarine specialist in the Royal Navy who commanded both the Portland and China Submarine flotillas and was Commodore Superintendent Gibraltar 1943–45...

, and joined the 1st Submarine Flotilla on 17 February 1922.

From 9 May to 14 May 1926, along with HMS K26

HMS K26

HMS K26 was the only modified K-class submarine of Britain's Royal Navy to be completed. One of six ordered, she was laid down towards the end of the First World War but not completed until five years after its end....

 and HMS L23

HMS L23

HMS L23 was a British L class submarine laid down on 29 August 1917 and moved to HM Dockyard, Chatham for completion. She was commissioned on an unknown date.HMS L23 survived a heavy depth charge attack by two German destroyers in February 1940...

, M3 was used to help supply electricity to the Royal Victoria Dock

Royal Victoria Dock

The Royal Victoria Dock is the largest of three docks in the Royal Docks of east London, now part of the redeveloped Docklands.-History:...

, Royal Albert Dock

Royal Albert Dock

The Royal Albert Dock is one of three docks in the Royal Group of Docks of east London, now part of the redeveloped Docklands.-History:The dock was constructed to the east of the earlier Victoria Dock by the St Katharine and London dock companies and opened in 1880...

 and King George V Dock in London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

, during the General strike

General strike

A general strike is a strike action by a critical mass of the labour force in a city, region, or country. While a general strike can be for political goals, economic goals, or both, it tends to gain its momentum from the ideological or class sympathies of the participants...

, in an action named Operation Blackcurrent. M3 alone kept four meat cold stores, two cranes, and many important pumps running.

Minelayer

On 15 October 1926 M3 was placed in reserve until 13 June 1927 when she arrived at Chatham to be converted to an experimental minelayer

Minelayer

Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...

, as a result of the Washington Naval Treaty

Washington Naval Treaty

The Washington Naval Treaty, also known as the Five-Power Treaty, was an attempt to cap and limit, and "prevent 'further' costly escalation" of the naval arms race that had begun after World War I between various International powers, each of which had significant naval fleets. The treaty was...

. The conversion was called a refit for political reasons. Her 12-inch and 3-inch guns were removed to make room for a large free-flooding superstructure extending over about 75% of her length. Two sets of rails ran along the pressure hull inside this structure, capable of accommodating 100 standard Type B contact mines. The mines were laid by means of a conveyor chain through a single large door at the stern.

The conversion was completed on 8 October 1928 at a contemporary cost of £10,235, and M3 finished her trials by the middle of November. Only 80 mines were carried initially, the remaining 20 being embarked later.

The minelaying machinery and mines added approximately 54 tons to the submarine's mass, and also had adverse effects on M3s diving ability - the time required to flood the large casing (which held 600 tons of water) meant that it took around 5 minutes to dive in calm weather, and at least 13 minutes in rough weather, and was dangerously slow to catch a trim. Rear Admiral Martin Dunbar-Nasmith, head of the Submarine Service

Submarine Service

A Submarine Service is the branch of a navy responsible for operating submarines.* Argentine Submarine Force* Royal Australian Navy Submarine Service* Royal Navy Submarine Service* Royal Netherlands Navy Submarine Service* United States Navy...

, was of the opinion in May 1930, that "...at present M3 is not efficient or reliable as a submarine and could not with safety be used in war".

M3 was originally to be scrapped in 1933, but the date was brought forward after the unfavourable reports of her abilities as a minelayer, and she was sold out of service on 6 February 1932, and was scrapped at Newport in April 1932.

Experience gained from the converted M3 was used in the design of the Porpoise-class minelaying submarines

Grampus class submarine

The Grampus-class submarines were a group of minelaying submarines built for the Royal Navy in the late 1930s. These boats are sometimes referred to as the Porpoise class from the single prototype, HMS Porpoise built in 1932. Five boats to a modified design were built between 1936 and 1938...

, which carried their mines in a single row.