The original 'Gangster Gun'. This was manufactured under licence at the Birmingham Small Arms Factory.
Originally called the trench broom as they were intended to sweep trenches clean of opposition, their cost was a problem as was the end of WW1 occurring three years before the Thompson was developed (1921) . Used by US gangsters as equalizers to superior police numbers in the inter war years and used by some of the most famous.
After WW2, These weapons were replaced by the crappy sten gun, WHY!!!!!!!. (because they were very expensive and fired different ammunition, that why!)
S.W.A.T Teams were also desparate to get a grip of some since they claimed the MP5 wasnt powerful enough.