It's exactly 80 years to the day that an act of mass trespass took place at Kinder Scout - now in the Peak District.
It was an important part of the long campaign to secure the right to roam in open countryside.
Some of the people who took part were sent to prison - having been accused of riotous assembly.
Two decades later the area became part of the country's first national park.
And the right to roam is enshrined in law in the Countryside and Rights of Way Act, 2000.
Among the people jailed was Tona (Anthony) Gillett, a 20 year old university under graduate, who died in 1992.
His son Jan Gillett from Leamington Spa in Warwickshire has been visiting the area for the 80-year commemorations.
Mr Gillett said:
"He and the others were put up before the bench in Derby. And the bench was stuffed with landowners and ex army officers and so on.
And it was a very formal prosecution. And the paperwork is all about riot. As if these people were trying to bring down the government. He drew himself up to his full height and said 'No My Lord, I would do the same again.
And so he was sentenced to two months in prison. I think he didn't serve two months. Nevertheless for a 20 year old under graduate that was quite a thing.
And after this event he always used to say that it helped him revise for his exams and he went to Cambridge instead of Manchester.
It would appear now, looking back after all those years that the National Trust and the Right of Access to Land Bill and so on, it was a pivotal moment. It really drew national attention to it."
Many people visiting the Peak District - locations like the highly popular Dovedale, run by the National Trust - have said they owe a debt of gratitude to campaigners like Tona Gillett.
Others say opening the hills has added pressures to the land - like erosion, dog attacks on farm animals, and the dropping of litter.
And there are calls for the tens of thousands of walkers to respect the countryside regions they are now free to visit.
Keith Wilkinson has the full report: