The recent UK demonstrations by students against the huge increase in university fees has provided the latest example of media coverage of such events: they are often presented as being motivated by violence which endangers the fabric of our society.
The police's stance is very simple – they claim that they are there to protect demonstrations, but that inevitably violence occurs. But my own experience suggests that this is a gross oversimplification.
Two or three years ago, there was a meeting in Parliament Square organised by those who opposed the Iraq war, at which a Member of Parliament spoke, together with two very senior UN officials who were involved in Iraq. The event was attended by hundreds of peace campaigners, many of them elderly, and all of them committed to peace.
The demonstration had been organised in connection with a plan to deliver a letter to the Prime Minister in Downing Street, and after the speeches were over the crowd began to move towards Whitehall.
But that same day, President Bush was visiting 10 Downing Street and the police were ordered to close Whitehall, preventing the letter from being delivered. As the crowd moved to enter Whitehall, they came up against a body of police. The pressure from the back pushed people forward and the police began using their batons on the crowd at the front.
As I was at the head of the protest myself, I saw what was happening – the violence of the police against the demonstrators was clearly visible and was very frightening.
It is in these circumstances that occasionally someone may pick up a brick and throw it – not that I saw it happen that day. But such an action would be taken as proof of violence against the police.
Similarly, the process of "kettling", in which police surround a crowd and prevent anyone from leaving, has caused trouble, since kettling is a form of imprisonment of demonstrators without any court justification.
There is no doubt that you will find a few angry people in any crowd, and kettling may bring this aggression out further. But then the media uses the inevitable clash as evidence that the demonstration is violent, which is not actually the case.
No government likes to find itself faced with demonstrations against its policies and as these recent pictures show, there are plenty of disillusioned citizens across Europe right now. Over Britain's long history, many significant gains have been brought about by such demonstrations – as with the recognition of trade unions, the campaign for the vote by the Chartists, and for votes for women by the Suffragettes.
Each of these campaigns was denounced at the time as violent. But it's interesting to see exactly how they unfolded. To begin with, the demonstrations are ignored; if they continue, they're described as absurd, and then if they persist, they are described as violent and the people responsible may be imprisoned.
Then comes a pause as public opinion realigns itself to support the changes being demanded. Once the government has finally got the message, you can't find anyone who doesn't claim to have supported the demands in the first place.
It's not possible to find anyone now who was opposed to the recognition of trade unions or to the principle of one woman, one vote. Yet it was only a committed group of campaigners who actually brought these changes about. There's no justification for violence – if protesters resort to it, it can turn public opinion against the cause.
Remember the way that public opinion shifted in support of men such as Gandhi and Nelson Mandela. Both are now regarded as heroes for the sacrifices they made to defend human rights. There is hardly any support now for the Vietnam war and public opinion is strongly opposed to the Afghan war.
This all goes to prove the importance of demonstrations and popular campaigns for peace, human rights and democracy.
We must expect far more demonstrations in the future and they must be seen as an integral part of political action in a democratic society. Without them, injustices would continue unchallenged and people would lose confidence in the democratic process by which such injustices are changed.
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