On Sunday 24th April 1932 about 400 ramblers walked to the summit of Kinder Scout in the Peak District, land owned by the Duke of Devonshire whose gamekeepers tried to prevent the trespass. Five ramblers were arrested for unlawful assembly and breach of the peace and were jailed for between two and six months. This turned the tide of public opinion and a few weeks later 10,000 ramblers assembled for an access rally.
These actions led directly to the 1949 National Parks and Access to the Countryside Act which established the National Parks, Peak District being the first, and started the process of providing open access to the countryside and to the 2000 Countryside and Rights of Way Act which enshrined a right to roam pretty much everywhere.
Rights are hard to come by.