https://aeon.co/essays/who-chopped-down-britains-ancient-for...
"This understanding has now been shown to be wholly inaccurate. Much of England had been cleared as early as 1000 BCE, some two millennia beforehand. The Bronze Age saw intensive farming on a scale that we are only just beginning to appreciate. As Oliver Rackham puts it in The History of the Countryside:
"It can no longer be maintained, as used to be supposed even 20 years ago, that Roman Britain was a frontier province, with boundless wild woods surrounding occasional precarious clearings on the best land. On the contrary, even in supposedly backward counties such as Essex, villa abutted on villa for mile after mile, and most of the gaps were filled by small towns and the lands of British farmsteads."
"Obviously there as loads more forest than now, but 1000 years ago it was about 15% forest, and now it's about 9%
This once popular belief or legend or myth connected to the forest myths of germany and Robin Hood and the idea of a primeval ancient woodland in the British deep dark past. Maybe also connected to a kind of romanticism of a past wild non-modern country.