one of the country's top investigative authors will be shedding light on the shadowy world of British military intelligence in his first appearance at Bewdley Festival.

Stephen Dorril, who lived in Kidderminster until he was 18, is talking on MI6, a highly secretive cog in the Government's foreign intelligence machinery.

As a dogged researcher of its history and activities, and a constant thorn in its side, Mr Dorril is well qualified to enlighten the audience with little-known and sometimes disturbing material.

He has written or co-written five books, founded a magazine dedicated to covering the security and intelligence agencies and worked as a consultant for numerous radio and television programmes.

Dorril, 47, who now lectures at Huddersfield University, traces his interest in the subject to when he attended King Charles I High School, then a grammar school, in the early 1970s.

"It was 1973 - the time of Watergate. I was always interested in American politics, the CIA and Vietnam," he said.

From 1980 - after acquiring a psychology degree and working as a probation officer - he started to focus on Britain and founded "Lobster", a "fairly serious journal about intelligence agencies".

With no background in such agencies, it has been a painstaking and gradual process to build up material and credibility, especially as the UK still has no freedom of information act.

"You reach a certain stage when people who used to work for these services start to take you seriously and you can interview them," Dorril explained.

His most recent book, MI6: Fifty years of Special Operations, took him three years to complete and two of them were spent researching.

He added: "Every book I've done I've had legal obstructions. On my last one I was threatened with an injunction by the attorney general to stop the book being published."

Dorril claims MI6 and MI5 routinely smear former agents such as David Shayler who try to "blow the whistle" on their past lives.

And he says many people do not appreciate the power such agencies can exert.

"They do make lots of cock-ups and simply don't know some things - which is why September 11 happened.

"But I know people - and have written about them - who've had their lives destroyed by this power.

"They can take away jobs, give bad references and bad credit."

However, he does still have time for life's lighter pleasures. He often watches his beloved Kidderminster Harriers play away in the north, and he is a regular visitor back to the town to see friends and family.

Dorril will be speaking at 2.30pm next Thursday at Bewdley Baptist Church. For tickets call 01299 403355.