Olivia Colman and Benedict Cumberbatch's secrets to successful marriages

Colman and Cumberbatch have been friends for many years

Olivia Colman and Benedict Cumberbatch have spent the best part of the last year swearing, shouting and sneering at each other.

Their latest roles see them play Ivy and Theo Rose - a wealthy couple once blissfully in love, who now find themselves in a marriage breakdown and bitter divorce battle.

Ironically, the relationship between the two actors couldn't be further from their warring characters - they're actually close friends, having met decades ago in a radio recording studio.

As I sit down with them the morning after the film's premiere, the pair, cups of tea in hand, are gushing over how great the other looked last night.

Colman thanks Cumberbatch for his support the night before as she admits she hates these sorts of events and parties. "If it's my party in my own house with people I know, then I love it," The Crown actress says.

Cumberbatch agrees that these events can be challenging as "you have to have those awkward conversations and really you just want to go and speak to your mum or wife."

"It is very heightened, odd and a bit weird but you have to just enjoy it and try to find the fun in it."

The Roses has been praised by critics for being "relentlessly entertaining"

After dissecting the night before, the enthusiastic praising of each other continues. Colman says she felt like a "competition winner" at points and Cumberbatch explains that their acting styles perfectly complement each other.

"I fret, she doesn't faff, she's really patient with my fretting and I love her non-faffing. We really do get on incredibly well," he says.

The Roses is an adaptation of the 1989 film The War of the Roses, which was directed by Danny DeVito and starred Michael Douglas and Kathleen Turner as a couple going through an increasingly acrimonious divorce.

In this new version, the sour marital conflict from the late 1980s has been transported into a glossy but volatile world of modern ambition.

Directed by Jay Roach and written by Tony McNamara, Theo is an architect whose career collapses at the same time as his wife's career as an up-and-coming chef skyrockets.

Resentment grows as Theo finds himself a stay-at-home dad, dedicating his time to training their two children to get into a sports scholarship school, while Ivy jets around America opening new restaurants.

Colman plays a high flying chef in The Roses

While their characters seem to detest every ounce of each other - "I like that he has arms", Colman's character says during one marriage counselling session - the actors are both happily married in real life.

Colman is married to producer Ed Sinclair and has three children. Cumberbatch also has three children with playwright and director Sophie Hunter.

'Don't throw knives'

Both married for a number of years, I ask them what the secret is to a successful marriage?

"Don't be complacent and keep the conversation between you going rather than thinking one of you is always right," the Sherlock actor says. "It's also important to be tolerant, understanding and never stop working at it."

Colman adds that she makes sure she and her husband always appreciate each other and are "being nice and checking in on each other".

They add that filming The Roses didn't make them think differently about love and relationships, but jokingly say they learned "not to have hard fruit in the house, don't throw knives or wear headphones in the bath".

The Roses is all about what happens when work, ambition and family life collide.

Both actors admit it's taken time to work at balancing career pressures and family life.

In the film, Ivy feels guilty for missing key moments in her children's lives because she's working, and Colman says this really resonates with her.

"From the moment you have a child, you'll have guilt.

"I took my eldest on set with me when he was six weeks old and I thought it would be easy but regretted it and even while he was on set, I felt enormous guilt because it didn't feel like the right environment for him to be in," Colman says.

Cumberbatch's character Dr Strange will return in Avengers: Doomsday

She adds that she turns down most jobs which are abroad and normally tries to be home every night.

Cumberbatch agrees: "The British industry is flying right now, so a lot of work comes here including a franchise we're both part of."

He's referring to the Avengers franchise in which he will reprise his role as Doctor Strange in the upcoming Avengers: Doomsday. Colman has previously appeared in Disney+ TV series Secret Invasion, as MI6 agent Sonya Falsworth.

The pair look at each other coyly, nervously giggling - there has been no announcement of Colman being involved in the films.

I ask if we can expect Colman to be involved, at which she says to Cumberbatch: "If you've made this happen because you've said this now I will be so thrilled."

The pair tease me by saying she's the new villainess but it's left unclear whether she will have a role in the new films.

'Relentlessly entertaining'

There are plenty of rom-com films, including those that chart the downfall of a relationship, but few manage to merge both themes in under two hours.

Most critics have praised the film - The Independent called it "relentlessly entertaining" in its four-star review, while The Telegraph said Colman and Cumberbatch are "deliciously savage".

In a two-star review, The Guardian said the actors were "let down by the overly glossy romcom-y sheen" or Warren Adler's novel, who wrote The War of the Roses, on which the film is based.

I get the sense that these two British actors aren't particularly interested in the reviews - Cumberbatch says the "whole project was based selfishly on us wanting to work together".

They're excited to discuss what they might do together next.

Cumberbatch says he really wants to do a play like Who's Afraid of Virginia Woolf or Much Ado About Nothing, but Colman is quick to shut it down saying: "I really can't hold a whole play in my head any more."

We might not know what the pair will act in together next, but one thing does seem certain, this isn't the last time they will be co-stars.