English makers were always looking for a marketing edge and as a result there was a mad rush during the 19th century and earlier to invent and patent thousands of different ideas to "improve" a gun. By far the majority quickly and thankfully slipped into obscurity. London, being the main cosmopolitan center of the country, was always considered to have craftsmen and products that were superior to the rest of the country. And they certainly didn't discourage that image. Competition was stiff between all gun makers but the London gunmakers inherited the "best" title. And competition between these top London makers kept them pushing forward trying to never be viewed as a second tier company. And indeed the results of this demanding market produced some of the finest arms the world has ever seen. There were many provincial makers aggressively competing with the entire industry and a number produced arms ever bit as fine as anything London produced but they never could overcome the cachet of "London best".
What is a best? I think the word itself is an oxymoron, since nothing made by human hands can ever be considered to be the best. Someone could always make it a little better. But in my mind it is a gun that stands out from all the rest as being nearly perfectly constructed in all respects, always bearing in mind the constraints encountered during the time of its manufacture. Every area of England outside of London produced examples of this work, Birmingham, Liverpool, Wolverhampton, Glasgow, Edinburgh, and many, many market towns.
The attitude that a best gun must be stocked to the fences, not have a through lump, etc., is the result of the homogenization of all the ideas preceding it having been sifted out and funneled through a narrow opening. And I think this thought process is wrong. Each gun, regardless of its mechanical process should be critically judged independent of the standard.