JAMES Spader’s knee is buggered.

The American actor explains that he injured it a few days previously while shooting his hit show The Blacklist and now he’s pretty much hobbled.

“I’m reminded,” he says, with a wry smile, “that I’m not as young as I used to be.”

Sitting in a nondescript meeting room on the show’s New York set, a hovering publicist attempts to get him to sit on an elevated chair to do the interview (surely a metaphor for Hollywood’s “us and them” mentality), but the actor is having none of it.

“I can barely walk,” he says, “so I think it’s better for everyone if I sit closer to the ground. I don’t want to injure anyone else by falling off a perch.”

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Right now, Spader is again at the top of his perch thanks to the success of The Blacklist, in which he plays the enigmatic FBI agent-turned-criminal, Raymond “Red” Reddington.

The show, which has hints of Kiefer Sutherland’s 24, has been a hit with fans thanks to its smart plot lines, unpredictable twists and turns. Ultimately, though, much of its success hinges on Spader’s tour de force performance.

“The fun of this show is it’s like a puzzle, but not like a puzzle where you empty the box and all of the pieces are laying in front of you. Instead this is a puzzle that we’re giving you the pieces as we go along. Eventually you can kind of put them together and they fit,” he says. “I don’t think I could survive on a show that there was an equation and you were solving that equation every week, I just couldn’t do that.”

Newcomer Hisham Tawfiq (who plays Dembe, Reddington’s right-hand man), says that watching Spader up close has been “a masterclass in acting”.

“It’s something that I don’t take for granted; I kind of just suck up everything that I see him do,” says Tawfiq. “Being the actor that he is, I just try to learn as much as I can working around him. And he’s just a humble man. I feel, like Dembe, I’m in the wings learning as much as I can from him.”

Spader, who has had an impressive career across film, television and theatre, says that these days actors have to be more versatile than ever.

“The business across the board has changed; the business of being an actor has changed,” he says. “Film, television and theatre used to be so compartmentalised. Now, everyone’s working in whatever genre they can — they have to. Because of economics, it’s all become one business now. I’ve seen a real sea change in terms of that.”

As far as his own career goes, the 54-year-old concedes that he’s been fortunate.

“I’ve been doing this for decades and I still have no idea how to operate within the business,” he states, plainly. “I just read scripts and decide what I’m interested in doing, and I understand that I’ve just been really lucky.”

Still, he says that he hesitated before taking on The Blacklist.

After spending five years on the drama, Boston Legal, he wasn’t sure if he wanted to sign on to another long-term deal.

“To be frank, yes, I was apprehensive about signing on for a network show,” he says. “I was definitely particular about what I was looking to do. I didn’t expect to end up on a network show, but the material was so good.”

Still, being on a show that shoots 22 episodes a season has been draining.

“I finished the first season of The Blacklist and I was exhausted because it was quite a sprint,” he says. “I needed to regenerate.”

Instead of putting his feet up, though, he hopped a plane to London where he shot the hotly anticipated The Avengers: Age of Ultron film, in which he gives voice to the villainous Ultron, an armour-crushing robotic monster.

For the veteran actor, the experience was an unexpected one.

“It was a different experience from any film experience I’d had because I was doing a character that was from the comic world — one that was being created through computer CGI. For me, wearing a motion capture suit and doing the scenes like that, was such a different process than anything I was used to. I actually found it really challenging.”

Now, in the midst of shooting season two of The Blacklist, he says that he’s in the dark as much as the audience as to where his character is headed (is he or isn’t he Lizzie’s father?).

One thing he knows will stay the same is Reddington’s signature fedora.

“It was my idea for him to wear a hat,” says Spader, “but unfortunately, now it’’s ruined fedoras for my life. I’ve always worn hats, but I’ve had to put my fedoras on the shelf now. I’m a bit over them.”

The Blacklist, Channel 7, Monday, 8.30pm