The National Farmers' Union (NFU) is holding a mass lobby of MPs with 1,800 of its members - three times as many people as originally planned - to urge backbenchers to stand up to the Government's plans to impose inheritance tax on farms worth more than £1 million.
Many more joined a separate rally in Whitehall as they protest against last month's Budget, which also sped up the phase-out of EU-era subsidies as funding is switched to nature-friendly farming schemes.
Among the farmers and supporters was Jeremy Clarkson, who owns the Diddly Squat Farm in the Costswolds.
NFU president Tom Bradshaw gave a speech to members taking part in the mass lobby ahead of their meetings with MPs, at Church House, Westminster, in which he became emotional at moments as he highlighted the cost of the policy on farmers, as well as food security.
5. Nigel Farage
Nigel Farage (right) with Simon and Freddie Poulter, four, during the farmers protest in central London over the changes to inheritance tax (IHT) rules. Photo: James Manning
6. Jeremy Clarkson
Jeremy Clarkson arrives in central London to join the farmer's protest over the changes to inheritance tax (IHT) rules in the recent budget with introduce new taxes on farms worth more than £1 million. Photo: Aaron Chown
7. Thousands at farmers protest
Farmers protest in central London over the changes to inheritance tax (IHT) rules in the recent budget which introduce new taxes on farms worth more than £1 million. Photo: James Manning
8. Farmers protest
Farmers have reacted over the inheritance tax changes for farming businesses, which limit the 100% relief for farms to only the first £1 million of combined agricultural and business property. For anything above that, landowners will pay a 20% tax rate, rather than the standard 40% rate of inheritance tax (IHT) applied to other land and property. Photo: Andrew Matthews