Actor Russell Crowe bulked up to play a 17 stone character - only to be told to shed the weight again - in preparations for his latest film, Master And Commander: The Far Side Of The World.
Crowe appears as an athletic soldier in the film
In the original books by author Patrick O'Brian, Crowe's character Captain Aubrey is the gigantic commander of the boat HMS Surprise.
Accordingly, Crowe - who put on 80lbs to play Jeffrey Wigand in 2000's The Insider - went on a mission to build up his weight. But six weeks before rehearsals began, the film's director Peter Weir changed his mind.
"Peter called me and said, 'look, I've been thinking about it - I don't want there to be need for a midshipman to be pushing the captain up the stairs, so maybe we should re-think where we are going in terms of size'," Crowe told the BBC.
"This was a little bit difficult, because I was already well on the way.
"But it was a quick turnaround - change of diet, exercise regime put back in place - and this decision was absolutely right, because you've got to see the captain as an active, engaged soldier.
"If we'd have followed the descriptions in the book, you would have ended up with Laurel and Hardy at sea."
The Master And Commander books - 20 in total - have acquired one of the most fanatical set of readers of any book series.
Bringing the first of these to the screen has taken 10 years and involved a number of changes in addition to the slimming down a beefed-up Crowe.
Most significantly, the story is now set in 1805 rather than 1812, as Crowe's vessel, the HMS Surprise, takes on the French rather than the Americans along the coast of Brazil.
Director Peter Weir has told the BBC that it had proved impossible to explain the 1812 war satisfactorily, and that O'Brian had "wished he'd started the series earlier so he didn't run out of history, or at least of the more interesting history of the Napoleonic Wars."
The film is still based on the basic plot of the book, however, as two huge battles sandwich a calmer central section in which Captain Aubrey's naturalist friend Stephen Maturin explores the Galapagos Islands.
"I just found Aubrey to be a fascinating character," Crowe stated.
He said Peter Weir had convinced him to take the part with description of Aubrey, "who had been on board a ship for most of his life and grown up in the Navy, and his thick, calloused hands sliding up and down ropes and climbing rigging, picking up a feminine instrument like the violin and extracting from it the most beautiful of sounds.
"That was the character description that kept me going through whatever problems I saw in the script."
But Crowe denied that playing Captain Aubrey showed he was only interested in powerful, masculine characters.
"For every leader that I may have played, like Jack Aubrey, there's an equal amount of internal men that don't have that kind of responsibility.
"For every movie that I've done set in a period, I've also done an equal amount of movies that are contemporary."
Crowe also said that the chance to work with Peter Weir - director of many films considered modern classics, such as Gallipoli, Witness, and The Truman Show - was the other key element of Master And Commander that persuaded him to take the project on.
"I grew up with his films, and I've had my experiences in the cinema where Peter has enthralled me, excited me, brought a tear to my eye," Crowe said.
"One of the things that you should do in this business is you should pay back the guys who have done it for you."
Master and Commander: The Far Side of the World was released in the UK on Friday.