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No mention here of whether any of these incidents were under VMC or IMC. It makes a difference because under VMC it's the pilot(s) who have the ultimate responsibility for aircraft separation.
Smilin Ed,
We're talking about the UK version of Class 'A' airspace here, where traffic is all
IFR. Separation is maintained between aircraft by ATC, whether or not the pilots can see out (OK, there's Special VFR available, but that isn't applicable in the discussion here).
TheOddOne