On a hot summer afternoon, a man with a microphone stands on a busy London street. He is a tubby figure and sports a black, bushy beard, flecked with grey. He is shrieking at passing shoppers, insisting they follow him - and save their souls.
Teams of young, tough-looking men - all clearly devoted to their leader - dart through the crowds, handing out leaflets and haranguing anyone who questions their message.
From the other side of the street, you could be forgiven for thinking this is a harmless, if colourful, example of citizens making full use of Britain's ancient tradition of free speech.
But there is nothing harmless about what is really going on here. For the man with the microphone is Anjem Choudary, branded the most dangerous man in Britain.