Though we can dig out information about delays when they are a day or two old, for something that far back it's nearly hopeless. The captain's advice should be taken at face value, however if ATC delays alone were sufficient to remove the connection then BA would be correct not to pay up. So it's going to come down to timings and details, and you're rarely going to get that at Customer Relations - they spend a few seconds on each case. So CEDR is probably your best bet if you feel that the technical issues were what prevented your conneciton.

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