I think it’s called the Robin Hood Tree because it was in a Robin Hood film.
Yeah, but the movie was presumably filmed there because they were looking for something that didn't have houses or whatnot in view, looked like it did during the time of Richard Lionheart.
I mean, that's probably part of it too, but I also feel like they wouldn't have filmed the scene at Canary Wharf.
Honestly, given that Robin Hood's home was Sherwood Forest, Sycamore Gap is about...checks Google Maps...about 172 miles by (modern day) road out of the way, too.
EDIT: Hmm. Apparently, Acer pseudoplatanus also didn't grow in Britain at the time Robin Hood was supposed to be running around, either -- it was introduced from central Europe, probably significantly later:
Some trees introduced a long time ago to Britain are now considered ‘naturalised’. There is a specific term for species present since 1500; an ‘archaeophyte’. Such species include beech (native only to south-eastern Britain), horse chestnut, sweet chestnut, sycamore and walnut.
Hmm. I was wondering if the National Trust would object to plantings -- I dunno if you can do that in national forests here in the US -- but it looks like they do plant stuff:
For only £5, you can plant a tree that will tackle climate change and support life for years to come. Your support will help to plant and establish 20 million trees by 2030.
1,000,000 saplings have been planted so far thanks to your donations
14 species of tree have been planted including oak, beech and crab apple
Donations to Plant-A-Tree will be used to plant trees on national forests throughout the U.S. and territories. You can select to have your donation go to where it’s needed most or to a specific national forest. Donations to where it’s needed most are received in the national office over the course of the year and are pooled and distributed annually to reforestation projects at various locations in the national forest system.