The Prince of Wales is giving an after-dinner speech to the gathering, and both the EU's environment and farming commissioners, who rarely speak on the same platform, are due to address the 75 participants, who come from all 15 EU member states.
The aim is to see if green groups can make common cause with the continent's beleaguered farmers, who fear subsidies are increasingly under threat in the move towards global free trade.
The organisers, a small and eclectic group of Britons, are campaigning for a massive shift towards payments for looking after the land in ways which maintain rural employment, wildlife and landscapes.
Oliver Walston, a wealthy Hertfordshire cereal farmer who is the main organiser, said: ''We want to see if, when environmentalists and farmers from across Europe come together, there is support for reform of this kind. Are we just a weird, Anglo-Saxon enclave of conscience-stricken rich farmers, or are we on to something bigger?''Reuse content