3 black silntly moving craft

i was young at the time maybe 9-10 i cant give a specific date as it happened many years ago, we'd been visiting my grandmothers house in forden near welshpool in powys, wales, we where traveling home back to llanidloes where we lived, before newtown on the main road welshpool side, i know the exact location. we notticed a large square object hovering at the top of some trees my father stoped the car and reverersed back to the layby where the object was, we parked under neath the object and were all looking out of the car windows up at it, it was a black square object touching the top of some pine trees, it made no sound, we sat staring at it for a couple of minutes before the object rotated slightly then sped of in the direction we had come from, my father turned the car around and chased after the object down the road 2 other craft came over the hills from the left they got behind the other craft and went off a terrific speed and where gone. over the next 2-3 weeks the top of the tree which the craft was hovering above died about a meter maybe 2 meters long, the trees still stand today and u can see the dead part of the tree. this was a life changing experience and i have been facinated by such things ever since. my farther described them as square helecopters and mother says they where diamond shaped, i agree with the my farther. later on in life i was watching a program called scoffields quest when they brought up a sighting of the 3 craft over england they described them much the same as what i saw, hightening my curouisity of what we saw that night.
Date is approximate.  PD