Franek ... In case Danny missed your question, I’m guessing Halkiew was flying Spitfires on 20 Sqn at that time.
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Gaining An R.A.F Pilots Brevet In WW II
I’m sure Danny described here the work they did, but I can’t find the post[s]. Perhaps it was someone else? IIRC they flew up and down as targets for Army AA (not with live ammo, though).