Around 6 million acres of private land will be opened up when the Countryside and Rights of Way Act comes into effect from Sept. 19.
While many of these green swathes are already popular with hikers, this month will mark the first time that landowners will no longer be able to demand they leave.
"This is a significant legal step which pushes back the centuries of landowners' dominance of our countryside," said Nick Barrett, chief executive of the U.K.'s Ramblers Association.
The protest has its roots in the Industrial Revolution era and the beginnings of democracy, when in the late 19th century Britain's workers began to demand more access to the countryside around their towns and cities.
The first freedom to roam bill came before Parliament in 1884, where it was knocked back yearly until 1914, when access to the countryside was allowed if landowners gave permission.
Now, with or without permission, people can walk on all land mapped as mountain, heath, down, and moorland, provided it is not cultivated, they are on foot, and they behave responsibly.
The new act "is a fundamental shift in presumption: that people's right to walk on land, the nation's land, should be enshrined in law," said Barrett.
Issue Still Debated
The issue, though, continues to inflame passions in a country where walking is the most popular recreation and where disputes over rural affairs, such as fox hunting, draw protesting thousands to London.
"There are a lot of people who are still upset," said Caroline Bedell, access advisor at the Country Land and Business Association, which acts for landowners ranging from the billionaire Duke of Westminster, one of Britain's richest men, to Bedell herself and her "few" acres.
It is the uncertainty of what could happen this month that has most landowners worried.
"You don't know if you are going to be invaded by a thousand people or nobody," she said.
The law puts Britain at the forefront of nations opening up land for walking, at a time when it is looking at ways to combat growing obesity.
Scandinavians enjoy almost unprecedented access to their countryside, but many other European countries, and the United States, have much tighter restrictions.
Ronald Pense, 72, is a U.S. citizen who now lives and walks in England.
"In the U.S. there is virtually no right of way," he said. "You can't go anywhere into private property."
Walkers can only go where the terrain has made it too difficult to settle or cultivate, leaving U.S. public footpaths peculiarly difficult, he added.
"So hiking in the U.S. involves walking up a hill in the morning and walking down it in the afternoon," said Pense.