Calvin, that rifle was made by Millard Brothers ("Milbro") in Lanarkshire, Scotland. The guns were made on original German pre-war machinery which was purchased and sent there by Allied occupation forces after WW2, so basically it was a copy of the pre-war German-made model 27.
The Scottish guns went into production in the early 50's I think. Milbro used the model 27 architecture as the basis of many later modified models, before going out of business in the early 80's.
Post-war German Diana guns were re-designed and made on new machinery. German Dianas sold in Britain carried the "Original" trade name because Milbro owned the right to use "Diana."
"Diana 27" is one of the longest-running name plates in airgun history. If you will scroll down a bit you will find a couple of posts that show several variants and describe their history and details:
http://www.network54.com/Forum/184474/thread/1186231614/last-1186231614/One+for+Doug--Diana+27%27s
http://www.network54.com/Forum/184474/thread/1186231676/last-1186621091/More+model+27+details