"When I was working as Hook I was in constant pain but I was able to use that for the character as his stump gives him trouble all day." He has to wear an evil-looking hook in the film. "It is as the writer JM Barrie described it, a razor-sharp claw. You look at it and you know what it is meant for and that is opening human bodies like a can of beans."
He can't remember who played Hook in the Empire show. "But that's because no one I have ever seen has played him in the way I do. He is a dangerous, dark, melancholic, angry guy whereas he has always been played in the past as a buffoon or clown - although very well played in that way!"
The film hit the headlines when the Disney corporation dropped out. "But there has hardly been a film where there has not been some discussion about who was financing it," says Isaacs.
In the event, three studios came on board. "When they saw the rushes they all wished they had done it themselves alone. They were proud of it and think it is going to do very well."
For Isaacs, now a father with 21-month-old Lily by his partner Emma, he is just pleased to have made a family film along with Harry Potter.
"Many of my other films have had violence, swearing, nudity and all kinds of stuff. Now I don't need to hide what I have been in from from my child and my godchildren.
Also get such kudos now when I go round to friends' houses and the kids go mental over me.
"It's much more fun because I always end up in a room with the kids playing games anyway!"
Alas, he is not in the next Harry Potter film - his character was not in the story. But Malfoy is in the next book and he's keeping his fingers crossed that the character will be in that film.
"You know, it's a bit of a scream to go into the make-up room and see the cream of the British acting world sitting there. Personally, I'd just be happy just making the tea for people like Maggie Smith, Alan Rickman and Gary Oldman."
