Agree. This article makes no sense in terms of the tree's "historic" value.
Hadrian's Wall is from Roman era Britain, it was constructed around 122 AD, to build a border wall between what is roughly England and Scotland today.
Robin Hood is a figure from folklore who likely never existed, but the stories are set during the time of Richard the Lionhearted was away fighting in the third crusade, so roughly a 1000 years later... 1190s A.D. or so. Nottingham, Sherwood Forest, Loxley, etc., are all nowhere near Hadrian's Wall.
18th century UK was the colonial era, when George III was taxing us too much for tea, so any tree planted during that time would have been grown around 600 years AFTER "Robin Hood's" heyday.
When Bonnie Prince Charlie invaded England on behalf of his father, the “Pretender” James VIII & III, stones from Hadrian’s Wall were used to build a military road near the wall...so much for respect for antiquities in the 18th century.