"Gangs of New York" has been buzzing through Martin Scorsese's mind for more than 30 years. He read Herbert Asbury's non-fiction book in 1971 and had a first-draft script by 1977.

Now, a quarter of a century and (at least) $100 million later, he finally has a film - forged by a production as anarchic and sprawling as the period gangster mayhem it chronicles.

The shoot was based in Rome - where production designer Dante Ferretti recreated the grimy, Five Points district of mid-19th century New York, on a vast set at the Cinecitta studios.

It served to ensure an authentic, enthralling period feel, but shifting such a big-budget enterprise overseas and away from the prying eyes of US journalists also fuelled wild speculation.

Rumours flew of blazing rows, fights, budget overruns and an errant, overweight star. Most of it is true.

First, the obvious falsehood. A cursory glance at "Gangs of New York" reveals that contrary to reports, Leonardo DiCaprio did not stuff himself stupid with pasta and turn into a lardy mess.

However, the "Titanic" star did find himself on the receiving end of a bawling out from Martin Scorsese for turning up late one day, and came to blows with co-star Daniel Day-Lewis in a fit of Method acting madness.

That the young star was drawn into so fully inhabiting his role is down in no small part to Day-Lewis. The British thesp ended a self-imposed five-year acting exile to step in for Robert De Niro as Bill "The Butcher" Cutting - and he replicated the "Raging Bull" actor's legendary dedication to his craft.

Over the course of an eight-month shoot, he didn't break character, talking in a New York accent, responding only to his on-screen name, and working out to Eminem at 4.30 every morning, in order work up the rage necessary to play the vicious gang leader.

But the biggest battle was not between DiCaprio and Day-Lewis, but Scorsese and producer Harvey Weinstein. The portly Miramax mogul was desperate to work with his filmmaking hero, but the set would ring with shouting matches as the pair wrangled over the ballooning budget (which rose from $80 million to $100 million).

Then, with principal photography over and editing underway for a December 2001 release, the terrorist attack on the World Trade Center halted production.

Upon viewing the finished movie, it's easy to see why. A bloody epic about civil strife on the streets of New York wouldn't have gone over a storm in the gloomy autumn of 2001.

Even the intervening 12 months haven't been without problems. Scorsese spiked the score of Oscar-winning composer Elmer Bernstein, and continued his running battle with Weinstein - this time over the movie's running time.

So now it arrives, its participants battered and bruised by a gruelling experience. Was it worth it? You decide.