Ah, the power of YouTube and freeze frame.

Here after 50 years of collating unit codes of the Spitfires used in the BoB film, a new one to add to the database. Airworthy Mk IX MK297 DO-R.

Recognition points are – Distinctive white patch on top cowling, distinctive black mark on air intake cowling, four blade propeller and turning, four aperture wheels, fish tail exhausts with mixture issue white staining.

Taxiing Mk XVI SM411 also carried the DO-R codes.

Many thanks for posting.

Mark