Anyone else see this?

Was walking on Tuesday 17/9/13 with friend on Lea Valley Navigation Canal between Markfied Park and the Riverside Cafe. We saw high above us what appeared to be a full size tree(roots cut off) being carried in the air by an object high above it. It could have been a helicopter but was too high to be identified as other than a small black star shape. As the two floated across the Lea, towards the North East they got higher and higher and the gap between them greater and greater until they went from sight. Any ideas? Clearly it would take a very heavy bit of aircraft to lift a tree to any height and it would be very expensive. Too dangerous to use a balloon....