I am staring at a pile of papers on my desk. It's 5 inches high. To anyone passing by, it's just a rather tedious heap of orange and blue folders. But to me, it represents a period in my life when I became utterly obsessed with making a single radio documentary. So obsessed that at one point my boss feared that I was losing my marbles.

It all started about 5 years ago. I heard about a legendary tale of escape and endurance, a book called The Long Walk. It tells the story of Slavomir Rawicz, a Polish cavalry officer captured by the Soviets in 1939. He was tortured and sent to Siberia then made a dramatic escape from the gulag and started a mind-boggling trek south. He and his companions walked 4000 miles across Siberia, Mongolia, the Gobi Desert and even traversing the Himalayas before reaching the safety of British India.

The book had been a bestseller and stunned readers across the globe. But there was one niggling question. Was it true? Perhaps arrogantly, I thought with the BBC's investigative resources we could find out. And so the madness began...

Radio 4 commissioned a documentary, and I started work early, looking up databases, sending out letters and emails and visiting potential interviewees. The brilliant reporter Tim Whewell was presenting the programme and as a Russian speaker, he had access to further sources. There were leads everywhere. The Polish museum in London? Check. A high school in Warsaw? Check. State archives in Belarus? Check. A veterans association in Latvia? Check. Human rights groups in Moscow? Check. US Army Department? Check.

And on it went. More leads. More dead ends. Lists of phone numbers. Conversations with elderly survivors of appalling atrocities - but of no relevance to our story. Leads. Dead ends. Some of the blind alleys were not surprising - such as the polite but firm rejection of requests for information from the French Foreign Legion. Others were entertaining - such as a sheaf of confidential wartime intelligence reports from across South Asia. As I leafed through the documents at the National Archive, I noticed that each month's despatch was accompanied by a comic poem written by the anonymous compiler.

And then there were some results. A bundle of documents from Pinsk! A hand-written note in a card file in Hammersmith! An amnesty paper from a Californian library! Amazing! Amazing! I remember jumping up from my desk and charging into my boss's office, eyes flashing as I told her the earth-shattering news of our latest discovery... and her gazing at me sadly, as she wondered when the mania would end.

The whole thing was probably made worse by the fact I had a comrade in madness. An independent American researcher called Linda Willis was on the same trail. Was it her incredible energy and resourcefulness that led her to write to hundreds of people, email many more and dig around in dusty archives across the globe over the course of 10 years?

Hugh Levinson - driven to the edge.

Or was she as bonkers as I was?

Well, we did find out some facts in the end. Linda wrote a book, Looking for Mr. Smith. And I finally managed to produce a documentary, which aired in 2006. Now Tim and I have made a new version of the programme.

One reason is that the great director Peter Weir has made a film inspired by The Long Walk. He decided to direct his movie after listening to our documentary and consulting us about what was true and what wasn't.

The other reason for a new programme, is that since 2006 we have made some tantalising new discoveries.

New discoveries? I can feel the madness starting again...

Hugh Levinson is producer of The Long Walk

• Listen to The Long Walk at 1330 on Sunday December 5th
• Spoiler alert: Hugh wrote an article for the BBC News web site in 2006 at the height of his madness. Don't read it if you'd rather not know the outcome of his original research before you've heard the programme.
• Rawicz's book, The Long Walk, was published in 2006.
• The film of the book is called The Way Back and is due for release at Christmas. The picture shows the stack of papers that torments Hugh.

http://www.bbc.co.uk/programmes/b00mjpcq

The idea behind the series was to find primary sources and to uncover original documents which might give some clues as to why the Bermuda Triangle myth caught on in the first place, and why it has endured for so long - and of course to get a sense of whether there is any truth in it. So it took a long time - about a year - to put together.

The real driving force behind it all was reporter Tom Mangold, with whom I worked extremely closely all through the research, recording and editing stages. It was his idea in the first place, and it was his passion and his extraordinary detective tenacity which made it all work. There is something rather attractive about the idea of setting a hard-nosed, investigative journalist the task of getting to the bottom of a myth, and it was quite something to behold when Tom gave some of the myth-mongers a courteous, fair but rigorous grilling.

One author we tracked down to his large house in Florida eventually unlocked the chain around his fence and invited us to talk in his garden about his part in genesis of the Bermuda Triangle 'mystery' . He ended up warming to Tom and finally admitting that he had 'spiced up' his book in order to make it more interesting.

There are three lines of enquiry throughout the series: first, we looked at the stories, articles and books which set up the myth in the 1950s and 60s, and some of those which have kept the pot boiling ever since; second, we spoke to historians and psychologists about the human need for mystery and conspiracy; and lastly we took several 'inexplicable' maritime and aircraft disappearances and did some thorough 21st century investigations into probable causes with the help of an air accident investigator and Lloyds Register in London.

Tom remains skeptical throughout, and virtually everything he uncovers suggests some very terrestrial and very human causes of the events and accounts of the Bermuda Triangle. However, we don't want to be complete spoil-sports and we did speak to some plausible people who remain convinced that they have experienced 'something weird out there". As ever, in my job, the real privilege was meeting the characters who gave us their time and their stories - and we met a lot, in the UK in the USA and in Bermuda itself.

And it was a privilege too, working with one of the world's best journalists and finest travelling companions. Indeed I have to admit, on the recording trip to the Triangle, more than one bottle of wine went missing without trace.

Adam Fowler is Producer of Inside the Bermuda Triangle: the Mysteries Solved

Adam sent this fascinating interview with a prominent Bermuda Triangle skeptic for exclusive use here on the blog:

Adam has also given me a full-length recording of the haunting song written and recorded specially for the programme:

• Inside the Bermuda Triangle: the Mysteries Solved is a five-part documentary made by Ladbroke Radio. Listen again on the Radio 4 web site.
• The Deadly Bermuda Triangle, one of the foundation texts of the Bermuda Triangle myth, by Vincent H. Gaddis, published in Argosy Magazine, February 1964.
• Picture, Bermuda Triangle Sky - 8, by Mike Powell. Used under licence.