To clarify, at the moment I can see on the radar a flight BAW2DP, which is on closer inspect BA792 flying LHR - TLS. Would I be correct in assuming DP refers to Toulouse? Or is it just some random letter assignment done when the flight plan is filed?
It is just random letters. Eurocontrol even advised airlines not to use letters which corresponds to destination,otherwise we all finish again with similar sounding callsigns.