Denzel opts for a light show

Denzel Washington is cheerfully humming a tune. It's not behaviour you'd expect from the man known for his stark portrayals of controversial civil rights activist Malcolm X or tough-talking bad boy Alonzo in Training Day, but the double Oscar-winner is anything but predictable.

Take his new action film 2 Guns, for example. As well as brawls, car chases and a pretty hairy run-in with some cattle, Washington does something much more surprising. He smiles.

"I was looking for a departure from heavier roles and when I read this script it really made me laugh," explains Washington, who played apartheid activist Steve Biko in British drama Cry Freedom and wronged boxer Rubin Carter in The Hurricane.

And with raging bulls, whip-smart wit and a rather dapper costume change, 2 Guns certainly marks a departure from Washington's previous role in Flight, as a pilot who snorts cocaine and downs a vodka before taking to the skies.

In the new film, he and co-star Mark Wahlberg, known for his performances in Boogie Nights, The Fighter and Ted, play a pair of undercover agents who work for the US Drug Enforcement Agency and the US Navy respectively. They have been brought together to infiltrate a Mexican drug cartel and recover millions of dollars.

Only neither Bobby Trent (Washington) nor Stig (Wahlberg) know that the other is also working as an undercover government agent, having given each other fake back stories.

"Bobby and Stig are lying to each other for half the film," says Washington, who has several scenes with Mission Impossible actress Paula Patton, who plays a conflicted government agent. "I'm not what I told him I am, and he's not what he told me he is."

When the plan goes to pot, their identities are uncovered and they're disowned by their bosses, Bobby and Stig have to work together to bring the cartel down and clear their own names which have been sullied by their swindling superiors.

In between all this, there are some rather ferocious fights. But Washington, no stranger to heavy-going action flicks with memorable parts in Inside Man, Man On Fire and Crimson Tide, is far from becoming big-headed about his prowess with a pistol.

"Mark is better with the gun than me. When he shot the chickens in the film, he was the business," says the actor, referring to a scene in which Wahlberg's character shoots three birds in the head.

"He had to snatch the gun from another guy, I didn't really have any gun play. And I noticed Mark had a little 9mm gun and was always smooth with it whereas I had a big 44mm gun and was like, 'Oh I've got to lift that gun up.'"

At a very lean 58, Washington, who came to acclaim with the 1989 civil rights film Glory and later won the Oscar for best supporting actor, looks like he can handle a 44mm gun. But a live, raging bull? Well that's a different matter.

"My back is better now but I had fun doing that scene," he says of a scene in which he and Wahlberg were hung upside down from the ceiling, beaten on the stomach with a baseball bat and then charged at by a seething bull.

"That bull tried to steal the scene," he adds, laughing. "He actually kicked his feet and started snorting at us, but thank goodness that the fence was between us. That was one big, mean animal."

While suspended from the ceiling, the duo have to use all their strength to lift their heads to their chests to avoid the bull pounding into their skulls. Such muscle power could call for a bit of boasting on set, but Washington is too long in the tooth for any shows of bravado.

"Me and Mark were tired after each take of the action scenes. In fight scenes I'd go, 'You win, it's all you!' There was no ego. It would have been easy in those fight scenes for someone to grip the other person a little harder but it wasn't about that," he says.

"A younger actor would have done that and said, 'Oh, what did I do? Oh sorry', and you'd say, 'Don't worry about it, we've got one more take'. Then in that take, you'd grip harder and say, 'Oh sorry. My bad. Cut!'"

For all his jokes, it's unlikely Washington would do such a thing to a plucky upstart. Settling into the interview, he natters about the weather before crooning away to himself in his low tuneful way. I feel lucky to hear this, I say. "So you should be," he jokes, smile firmly in place.

Away from the screen, he has a good deal to smile about too. He's just celebrated his 30th wedding anniversary to wife Pauletta and the couple's four grown-up children are a constant source of pride for this devout Christian.

"My son John-David is fulfilling my dream, playing football like I'd always wanted to," Washington has said. "My daughter Katia is at Yale, a place where I didn't dare apply. I dig seeing them do their thing. They live well, but we don't just give them anything they want."

Surrounded by wealth, good living and fanfare, their father could have become high and mighty. But asked what his job involves he shrugs his shoulders and deadpans: "Swimming a bit, walking across the desert, shooting some bad guys and wearing gold teeth. It's all in a day's work."

Extra time - 2 Guns

:: Denzel Washington's wife offered to babysit for Mark Wahlberg's four children while the two actors were filming.

:: 2 Guns originally started life in 2008 as a five-part graphic novel by writer Steven Grant and artist Mateus Santolouco.

:: Washington disguises himself as a naval officer in the film but says the fabric was too itchy for his liking: "I need a nice gabardine that just flows, or a Tom Ford outfit."

:: Boston-born Wahlberg improvised many of the lines in the film.

:: Washington says that Paula Patton, with whom he worked with on 2006 film Deja Vu, is the toughest of the three actors.

:: 2 Guns opens in cinemas on Friday, August 16