An alarm was triggered on the BA plane's flight deck

BA Flight 202 from Detroit to Heathrow was flying over the county when the near-miss happened.

It is reported that an American plane was ordered to descend by flight controllers.

This brought it close enough to trigger the Traffic Alert and Collision Avoiding System on the flight deck of the BA jet.

The BA plane then climbed to avoid an accident.

British Airways says an air safety report has been filed and the incident will be investigated by the authorities.

The National Air Traffic Service said there was no risk to passengers on board the two planes.

Controllers based in Hampshire said the planes were travelling in the same direction at the same speed, with at least a mile-and-a-half between them