4 mk I bayonet, much like other weapons at the beginning of World War II, was high quality.

4 mk II bayonet the design was further changed in 1942 to save costs and disperse production by making the blade and socket separately and this became the bayonet No.

4 bayonets of all marks were produced during World War II.

4 bayonet was simple to make and there was no spare production capacity in UK government weapons factories local production in the UK was contracted to private companies that did not usually produce weapons.

4 mk II bayonet were based abroad being The Crown corporation Small Arms Limited based in Long Branch in Toronto, Canada and Savage Arms out of their facility in Chicopee, Massachusetts in the United States.

[2] The Crown corporation Small Arms Limited was a Canadian government weapons manufacturer and Savage Arms who also produced Lee Enfield No.

4 mk II bayonet to provide to the UK under Lend-Lease.

4 mk II* was produced by four companies of which three were in England which were Prince-Smith & Stells in Keighley, Yorkshire, Howard & Bullough in Accrington, Lancashire, Lewisham Engineering in Ladywell, London and one in Northern Ireland, Baird Manufacturing from Belfast.

[2] Normally Prince-Smith & Stells and Howard & Bullough manufactured industrial machinery and Lewisham engineering was solely founded to make the bayonets.

[2] Roughly 1300000 No 4 mk II* bayonets were produced the majority by Smith & Stells who made a million and the other manufacturers roughly made a 100,000 each.

4 mk III bayonet was produced in relatively small quantities by one manufacturer, Joseph Lucas Limited in Chester Street, Birmingham.

[2] Joseph Lucas made automotive components before the war.