Just a comment on the article - if you look at the photo of BS/BF273 in Spitfire at War 3, it seems to have the converted Rolls Royce top cowl, with the bulges just above the rear of the exhaust.
Also Gailtzine describes it as a 'Cambridge Blue', not an Oxford blue (Oxford is the darker of the blues in the RAF rank insignias)
As BS274 also caried the wrong serial for all it's life as 'BF274' I do wonder if it was a phonetic error at theRolls Royce factory!!
This is just what happens (again :/) when you write something out of memory rather than double-check with the source. Of course I meant Cambridge blue! Thanks so much for pointing it out.