We just filed a claim with BA for a delay of five hours from Calgary under EU regulations. No qualms acknowledged straight away and paid within 48 hours, brilliant service. They also fed and watered us at Calgary and gave advanced notice via text the flight would be delayed although we were already en route to the airport! On a previous trip the delay was due to adverse weather but they still gave us a first class Hotel in Vancouver and fed us until the flight the next day.
Top marks to BA from us!