Jacob Ecclestone at the time of writing was Assistant General Secretary of the Writers' Guild of Great Britain. He is not a member of Yorkshire Playwrights

In a previous existence I joined campaigns against censorship and the oppression of journalists - issues like the Northern Ireland broadcasting ban, the Official Secrets Acts, the murder of The Observer's Farzad Barzoft and Israel's slow torture of Mordechai Vanunu. There were always plenty of cases, both domestic (where the censorship is mostly of the velvet variety) and abroad (where it was generally prison or an unmarked grave).

It was partly out of a sense of duty, then, that I went to the West Yorkshire Playhouse in Leeds at the end of March for a conference billed as "Writers in Chains". Out of ignorance, I expected more of the same. Instead, I was introduced to new and subtle varieties of censorship and persecution with poets and playwrights as the voices to be silenced.

Organised by Amnesty International and Yorkshire Playwrights, the conference lost much of its international flavour when the main speaker failed to arrive. Fortunately, in her place, we were treated to a brilliant tutorial on how the Lord Chamberlain lobotomised British theatre for most of the twentieth century. Dr Steven Nicholson is the head of theatre studies at Huddersfield University and is now tackling the second volume of his history of censorship in the British theatre.

Even though the office of Lord Chamberlain was finally abolished by Harold Wilson's government in 1968, it was salutary to learn how the licensing of public performances of plays operated. First, it had the total support of theatre managers; second, since the Lord Chamberlain never had to give a reason for refusing a licence the system soon generated self censorship among playwrights; third, one of the principal purposes of licensing was to ensure that "social harmony" was maintained. The theatre was there to soothe people and plays which made people think were discouraged because, by definition, new ideas can be dangerous.

Dr Nicholson, who has been patiently working his way through hundreds of boxes of files relating to thousands of long forgotten plays, ended with an appropriately local example. Within three months of Hitler coming to power in Germany in 1933, a Leeds playwright, Alan Peters, had written a play attacking the Nazis. The Lord Chamberlain took the precaution of asking the Foreign Office what they thought of the play - pointing out that that it was "only going to be put on in Bradord." The Foreign Office advised against giving the play a license and wrote that "the persecution of the Jews is not our concern." The play was finally performed six years later in September 1939.

"The real art of censorship", said Dr Nicholson, "is that it remains unseen."

Jack Mapanje had a different, more physical, experience of the price to be paid when writers are seen as a threat. Although he was head of the English department at the University of Malawi and an internationally respected writer, he was carted off to prison for offending Life President Hastings Banda. Yet there was more humour than bitterness as Mapanje talked about his first days in prison, how he had failed to see the warning signs of what was about to happen, the idiot distinctions that the censors managed to draw between removing his books from libraries and formally banning them!

Playwrights can be silenced in so many different ways. As well as reading his "Whatever Happened to Betty Lemon?", which was a treat in itself, Arnold Wesker handed us all copies of his "Theatre Cheats - An Open Letter to Trevor Nunn in Two Acts". Although two long to report here, it makes interested reading and can be found on www.arnoldwesker.com

John Arden talked about the work of an Algerian playwright friend, who was murdered by religious fundamentalists, and about how he and his wife, Margaretta D'Arcy were harassed under the Prevention of Terrorism Act because of their unpopular political views on the conflict in northern Ireland. Censorship comes in many forms, one of his plays losing an Arts Council grant for no better reason than the design of an advertising poster. Arden asked us all to be alert: "Whenever you hear that a writer has been arrested, don't stop to ask why. The first thing to do is protest."

.... and finally, Trevor Griffiths, described somewhere as a "long-time member of the awkward squad." For Griffiths, who has been working for years to bring his Tom Paine script to the screen, the "marketplace is the great censor in the sky."

Having sat through a lot of negotiations on behalf of the Writers' Guild when script alteration clauses were being discussed, I warmed to his plea for playwrights to fight against changes to their work unless as a result of discussion and agreement. He talked also about the censorship of one-production and the censorship of no production at all. Why, he wanted to know, had there been no plays about Ireland or the miners' strike of 1984-85? "The record of British playwrights in the context of Ireland and the miners' strike is appalling," he said.

I count myself lucky to have been at such a gathering.