at the top of the tree
(informal, figuratively) At the highest level.
A coconut plucker who climbed a coconut tree at the Wadduwa Police Station on Sunday (22) fell unconscious while at the top of the tree. Source: Internet
Some paintings in the present exhibition reveal the influence of mythology, too: the fox, having failed to reach the grapes at the top of the tree, claiming they are not ripe anyway. Source: Internet