It's one of the greatest stories ever told. The legend of Helen of Troy has enchanted audiences for the last three thousand years. In May this year a Hollywood film staring Brad Pitt and Orlando Bloom will be launched in Britain. But is there any reality to the myth? Horizon has unprecedented access to the scientist with the answers.

Since 1988 Professor Manfred Korfmann has been excavating the site of Troy. He has never before spoken at this length. He has made amazing discoveries - how large the city was, how well it was defended and, crucially, that there was once a great battle there at precisely the time that experts believe the Trojan war occurred.

But who had attacked the city and why?

Horizon then follows a trail of clues - the ancient tablets written by a lost civilisation, the sunken ship rich in treasure, and the magnificent golden masks and bronze swords of a warrior people. The film reaches its climax in a tunnel deep beneath Troy, where Korfmann has made a discovery that may reveal, once and for all, the truth behind the myth.

The story that emerges is one of great passion - but not, it seems, about love.