The most common reason for disruption at London Heathrow is weather. The types of weather that have the biggest impact on airline operations are thunderstorms, fog, ice, snow and strong winds (both on the ground and on approach to the airport). When London Heathrow is affected by adverse weather, Air Traffic Control reduce the number of flight departures and arrivals. Ground operations are also affected due to poor visibility and other safety issues. This results in delays and cancellations.
But what has the main cause of disruption at LHR got to do with the cancelation of a flight between LGW and NCE???