This is what is know as a “Parish Pattern”, in this case King’s pattern. These were patterns not registered to a particular maker. Often the blanks were made by a particular manufacturer, in the case of this pattern, in their thousands, and sold to another company to be plated to their own specifications.
As Trev says, the British Standard mark puts it to a fairly modern date, and I recall George Butler & Co. proudly claimed, in their marketing, to be the only cutlers and silversmiths working to this standard. They were taken over by Arthur Price in 1994.