Thousands of farmers, from farms of all sizes, stood shoulder to shoulder, generation to generation, to highlight the impact this would have if brought into play.
Organiser Olly Harrison made the opening speech, spurred on by a cheering crowd.
He said: "Is it the beginning of the end of UK farming or is this the beginning of some direct action to save this farming community we all love and feeds this nation every day?
"They think they can replace us with imported food, but they cannot."
He added: "Do the Government even know where food comes from?"
Supporters from outside the farming sector also showed up in support of farmers.
One attendee said: "I am not a farmer, but this is important."
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Various speakers made their plea on stage, including fellow organisers Andrew Ward and Martin Williams, Baroness Kate Rock, author of the Rock Review who spoke on behalf of tenant farmers and Clare Wise, whose family have farmed at Manor Farm near Darlington, County Durham, since 1875.
In a passionate speech to the crowd, she told Prime Minister Keir Starmer to ‘buckle up because you are not going to win this fight' and that she would fight to protect her farm with ‘every last breath'.
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Jeremy Clarkson
High profile figures came out in droves too, including Reform leader Nigel Farage and TV farmer Jeremy Clarkson who was, he said, advised by doctors not to attend due to his recent health issues.
He highlighted the endless navigation of policy that farmers face – a lot of ‘complication and endless costs' for ‘very little money.'
He asked the crowd to raise their hands if they were from a family farm and asked those who thought they were going to be unaffected to lower them.
"Thank you. My case rests," he said.
Agricultural Property Relief
"I want to finish with a message to the Government: For the sake of everyone here, and for all the farmers stuck at home paralysed by a fog of despair, I beg of the Government to be big, to accept that this was rushed through, and it is a mistake and to back down."