I believe there's one of those in London On in a park close to where my folks lived for some time. My dad called it a Ram...he would have known...
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The Royal Small Arms Factory was at Enfield and built alongside the River Lea (or Lee, both are correct). The river originally supplied the power to the water mills which supplied much of the motive power.
Enfield is not on the Thames as the article states, but 12miles to the North, The factory actually lies on the Meridian, due North of Greenwich.