The large flat area of the Parade Ground is where vast crowds gather at rallies to listen to political speeches on important issues of the day. The biggest rallies recently were against British military action in Iraq and the government's proposals to ban fox hunting.
The first large rally was in 1855 when 150,000 people protested against plans to stop shops opening on Sundays.
About 40 policemen tried to silence one of the speakers. A riot followed and 104 people were arrested. But the Sunday Trading Bill was withdrawn next day and Hyde Park became the place for people to raise their grievances.