You might say he's the British answer to America's Phillip Seymour Hoffman.
On the occasion I suggest it, the notion is met with a wry laugh.
"Yeah, he is brilliant and it is an honour to be compared with him. If anything, I'm striving to get to that same place, where my acting is completely free and natural," he says.
Marsan has been travelling that road for some 15 years now, after turning his back on a printing apprenticeship to focus on theatre and television.
What started as bit-parts in programmes such as The Bill and Grange Hill is rapidly reaping dividends.
Marsan's powerful personae attracting the attention of film-makers across the Atlantic, even if those at home have been slow to cotton on to his burgeoning talent.
"It's funny, you know. I played that part as Rev John in 21 Grams, which was nearly six years ago but it's only now that I am starting to get asked about it in almost every interview that I give," Marsan says.
Part of the reason for the slow-burn of Marsan's career to date could be his ability to ghost so effectively into different characters without waving his own placard.
"Well, that's my job," he says. "My role as an actor is to disappear. I don't crave celebrity, but I don't mind it either.
It has been really interesting to be suddenly forced into the limelight.
"When I did 21 Grams no-one knew it was me. The occasional actor would ask, but it's only recently that attention has been focused on that role, especially as I have achieved greater celebrity through other roles."
As a graduate from one of the United Kingdom's leading drama schools, Marsan's early foray into television was significant for his typecasting as a small-time criminal.
"I guess my objective has always been to stay in work, so I was not too precious about the parts I was cast for. When I started, my acting was pretty raw and fortunately, that was what casting agents wanted.
"I'm from a hard part of London and brought up in a council estate so when anyone met me they heard the accent and that was it. I suppose idolising [fellow British actor] Ray Winstone didn't help either.
"There were a bunch of us who really wanted to be gangsters, but you soon realise that there is only one Ray Winstone.
"Now I get offered certain roles based on my appearance. I mean, I've got a funny face. What can I do about that . . ? It gets me work."
Since those formative days as a mugger, thug, and yob, Marsan has not only impressed in 21 Grams, but has appeared in Martin Scorsese's Gangs of New York, Mission Impossible III, The Illusionist and the soon-to-be-released Will Smith super-hero epic, Hancock.
But for all his stateside success, the actor seems happy to remain resident in Blighty.
"I have thought about it, but I have a young family with three children under 3, so I have to consider where it will be best for them.
"The funny thing is, you make the move to LA and then you end up making films in Vancouver. I'm not saying it will never happen, but at the moment, I'm quite happy making television and film in Britain and picking up work in the United States when it comes up."
Marsan's recent efforts in British film include Happy-Go-Lucky and Grow Your Own, both of which involved quite different idiosyncratic roles.
"Well, working with Mike Leigh is quite unique, as there is never any script to start with," Marsan says.
"When we were making Happy-Go-Lucky I had no idea that my character Scott was going to turn out the way he did.
At the time, I thought I was creating the reincarnation of Travis Bickle [Robert De Niro's character in Taxi Driver]!
"As it turned out, Happy-Go-Lucky was a comedy and Scott was someone to laugh at, or feel pity for, rather than be fearful of.
"Grow Your Own was a totally different experience, as the script written by Frank Cottrell Boyce (24-Hour Party People/Tristram Shandy) was so good that my job was simply to serve the writer. As an actor with a tight script you can never improve the writing, so you look to achieve the best for the writer's vision."
In Happy-Go-Lucky, Marsan plays the part of a driving instructor - the sort of job most people have at least witnessed in action.
Though when you are working with the mercurial Leigh, that does not necessarily mean it is straightforward.
"As I said, working with Mike [Leigh] is really challenging, as you are not given a whole lot to work with. I did actually spend some time with driving instructors to analyse their methods and can honestly say I struck no-one like Scott [his character in the film], though I was told that they exist.
"Friends of mine who have seen the film can't believe it is me, as apparently my personality is so different, but my wife has great delight in telling people that I actually do drive like that!
"In the film Marsan sets up one of the most amusing pieces of repeated dialogue when teaching novice drivers to monitor their mirrors with the constantly repeated mantra of "en-ra-ha", indicating the triangle completed by the two wing mirrors and the rear vision mirror.
"When we were in pre-production, it occurred to me that it would make a nice analogy, as Scott is a paranoid conspiracy theorist. Once I started using it, Mike wouldn't let it go and insisted that it stayed as part of the final script.
"It is a popular conspiracy theory that the Eye of Providence shown atop an unfinished pyramid on the US $1 bill, indicates the influence of Freemasonry in the founding of the United States," Marsan adds by way of murky explanation.
By comparison, Grow Your Own looks like a great film to be part of, requiring nothing of the rage Marsan summoned for Happy-Go-Lucky.
This time around, Marsan had to find a way to bring the socially awkward but endearing Little John to the set.
"Well, it's a really authentic slice of allotment life in Britain. The set was so perfect that every day I was convinced I was going to work on a real allotment, which was really special.
"The allotment itself and its uncertain future is really an analogy for the situation that the various characters find themselves in.
"Grow Your Own is an issues film that taps into common concerns faced by normal people daily. That inherent fear of the other is certainly fertile territory for film-making, and Frank Cottrell Boyce's script resolves some of those issues via some really good characters."
Those characters, are brought to life by an ensemble cast of great British acting talent.
"I had worked with some of the cast before," Marsan says, "but I always relish the chance to act alongside Philip Jackson, who I remembered as a kid.
He played Greaves on this series called Scum and I always remembered him as a bastard with squeaky shoes.
"Actually, one of the best actors working in Britain at the moment is Benedict Wong. He's absolutely brilliant and Grow Your Own was a great chance to observe him at work."
The premise of the film is drawn from a family refugee support project in Liverpool.
The actors did not get to visit the project as part of their preparation "but some of the people involved with that project visited us on the set to share their experience," Marsan says.
A rapidly expanding CV and offers of work in the US means Marsan is in a position to compare and contrast the styles of some of film-making's top directors.
"Well, obviously, as I have mentioned, Mike Leigh has his own unique way of working which is quite an experience in itself. Martin Scorsese was incredible. He is unbelievably well researched, so that when he begins a shoot he knows the subject inside out, which was really important for Gangs of New York."
He has also had an insight into the different approaches on the two sides of the Atlantic.
"Well, the major difference is down to the two types of actors. American actors are a lot freer than their British counterparts, they feel OK to explore and serve their own mental processes, which is why they will try and get away with mumbling if it fits their idea of the role.
"British actors are reliable; they learn the lines and dodge the furniture, so to speak. They serve the writer well, but sacrifice some of their freedom in doing so.
"There are always exceptions, like Timothy Spall and Jim Broadbent, for instance. Spall is absolutely fantastic the way he creates a character."
Among the US talent with whom he has shared the set, recent Cannes best actor winner Benicio Del Torro gets a further nomination for his craft, from Marsan.
"Benicio Del Torro, no question. I worked with him on 21 Grams and he epitomised this idea of freedom. He was so natural that sometimes you never realised when he was actually doing a take, which can be a little unsettling until you get used to it.
"I have never worked with him, but I gather the same can be said for Phillip Seymour Hoffman.
"He serves the writing, but that does not limit him from where he takes it."
Having covered northern hemisphere acting opportunities, it seems only fair to ask whether Marsan has any plans to work his way south - perhaps in New Zealand, perhaps on The Hobbit?
"I have no offers to work on any productions in New Zealand at the moment," he says.
"But in this game anything is possible. It's interesting that you should ask about the connection with New Zealand and that next Tolkien instalment. I was reading an online forum and someone said that I look like one of the characters.
"I'm not entirely sure if that is a compliment or not."
So does Marsan read Internet postings often?
"Yeah, it's like when the wife's gone to bed.
Other men surf porn on the Internet - well, actors check out the Internet Movie Data Base [imdb].
"You have to have a thick skin. If you don't like the hype, then don't try and climb mountains."
I didn't want to ask this but after Marsan has mentioned online forums, I tell him I have read a posting where the writer stated that he spits in every film he is in. He laughs.
"That could be true, you know. I've never thought about it, but if I do, I certainly don't mean to."
And with that, the extremely affable Eddie Marsan heads back to his hectic family life and episodes of The Tweenies.
With a workaholic ethic and the ability to morph seamlessly into different roles, it won't be long before Marsan becomes a household name. Just don't expect that celebrity to get in the way of his craft.
Mark Orton is a Dunedin film-maker.
• Freebies
We have Grow Your Own prize packs to give away.
Each prize includes: a double pass to the movie, Blitzem granules, Thrive all-purpose plant food, an insect gun, a Yates Garden Guide, a wallchart and a vegie guide, vegie seeds (including broccoli, carrot, cauliflower, celery, spinach) and Black Magic seed-raising mix, together with a Tuscan Edge planter.
To enter the draw, write your name, address and daytime phone number on the back of an envelope and send it to Grow Your Own, ODT Editorial Features, Response Bag 500015 Dunedin, or email playtime@odt.co.nz with Grow Your Own in the subject line, to arrive before Thursday.
