Protest can come in many forms, from the picturesque and frothy to the courageous and political. Yesterday a group of angry brides marched on Canary Wharf to complain that HSBC had ruined their wedding day. Only a handful took part, but they captured the cameras' attention. On the same day, on the other side of the world, four young people from Britain and America staged a more daring demonstration, climbing up floodlighting poles to unveil a Tibetan flag in Beijing. Their protest was seen by millions.

The unblushing brides had a point: if the bank had not insisted on refunds for the 100,000 guests disappointed when Wrapit, the online wedding list service, went into receivership, some of those orders could have been completed. But the gowns, morning suits and wedding tackle made another good one: a witty and colourful protest wins the attention and sympathy that eggs and rotten tomatoes can never command.

A good protest needs planning, guts and money. The aim is to capture the public imagination. This may mean dressing up - as a bear or a badger, in rubber masks of G8 leaders, or even going naked. It may involve props, such as the milk churns and manure favoured by farmers. It may even risk breaking the law, such as halting a coal train or abseiling into the BBC newsroom.

Political protests are the riskiest, but get the headlines. The action outside the Bird's Nest in Beijing needed months of planning and considerable ingenuity. It is hard not to admire the way that four young protesters made their point in the face of the mighty Chinese Olympic security machine. Their success, and their perfect timing, are a reminder of what freedom should mean.