Queen guitarist Brian May has led several hundred black-and-white-clad demonstrators through the streets of London, urging the government to scrap plans to cull thousands of badgers.
The cull, which started in two areas of southwest England on Saturday, will see up to 5,000 badgers killed in a bid to combat tuberculosis in cattle.
But animal welfare groups are outraged by the plan, claiming it is inhumane and will do little to wipe out the disease.
Bovine TB spreads from badgers to cattle, and farmers are forced to slaughter thousands of infected animals every year.
But May, 65, said there was "not a shred of reason" for the culls in Gloucestershire and Somerset in southwest England, and delivered a 235,000-signature petition against it to Prime Minister David Cameron's office at Downing Street.