This was the subject of the History Channel Craig Charles S01E01 UFO Conspiracies program.
The UFO spotted was a pyramid-shaped craft which was chased , attacked and supposedly shot down by UK military aircraft. There was a huge explosion reported and trees in a nearby forest were damaged at about the 20ft height. The main witness has taken 3x lie-detector tests. She watched the incident with her neighbour friend on the night of the 26th Feb.
The UK's MOD has declined to give any details citing National Security as the reason but changing their story a number of times since the original event. For 3 days prior to this event, there were military craft over flying the area, almost as if they knew something was going to happen but did not know exactly where it would happen. After the incident the main witness was warned to keep quiet and there was a group (photographed) which conducted a thorough search of the area, staying overnight in tents.
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