CND's "Ban the Bomb" symbol is 50 years old tomorrow. It made its first appearance on a chilly Good Friday as thousands of British anti-nuclear campaigners set off from London's Trafalgar Square on a 50-mile march to the government's weapons factory at Aldermaston.

The demonstration had been organised by the Direct Action Committee Against Nuclear War (DAC) and the Campaign for Nuclear Disarmament (CND) joined in. Gerald Holtom, a designer and former World War II conscientious objector, persuaded DAC that they needed an image to express their aims. To create this he used letters from the semaphore - or flag-signalling - alphabet, super-imposing N (uclear) on D (isarmament) and placing them within a circle symbolising the Earth.

The full story is told in Ken Kolsbun's new book, Peace: The Biography of a Symbol. There's also a fascinating article about it on the BBC.

They interview peace historian Lawrence S. Wittner who says that "it is still the dominant peace sign," a fact partly due to its beautiful simplicity. It's perfect for spraying on walls and is a universally recognised symbol of peace and resistance to repression.

As Wittner says, although people are still fighting wars - this weekend is also the fifth anniversary of the invasion of Iraq - there has not yet been a nuclear war:

"There are many ways in which nuclear war has been prevented. The hawks say that the reason nuclear weapons have not been used is because of the deterrent. But I believe popular pressure has restrained powers from using them and helped curbed the arms race."

I agree that popular movements have played a big role in preventing nuclear war. But I would also argue that fiction and film brought the unique horrors of nuclear war alive in people's imaginations. The role of writers like HG Wells and Peter George (aka Peter Bryant), whose novel Red Alert was the basis for Stanley Kubrick's Dr Strangelove: or, How I Learned to Stop Worrying and Love the Bomb, is often forgotten. They too helped prevent war.

A peaceful Easter to you all!