The Treehouse

When I was asked if I could build a treehouse, I was certainly interested and love a challenge to say the least.
The idea was two levels. The first level was for the grandchildren to have some somewhere to safely play. The second level, for the grown ups to enjoy a G&T while watching the sun set.
With no other drawing or design ideas I was left to my own imagination to create this.
One feature was, not one single mechanical fixings penetrated the tree. It had been designed to move with the tree as it grows and after 4 years I came to inspect the tree house and found it was as strong as ever.