In need of a caffeine boost? Sienna Miller flaunts her long legs in a pair of high-rise trousers after partying until the early hours with Ben Affleck 

She partied into the early hours with her co-star Ben Affleck at the Live By Night premiere the previous day.

But Sienna Miller showed little sign of her big night out when she stepped out bright and early on Thursday morning, arriving at the Global Radio studios in London looking remarkably fresh-faced.

The 35-year-old actress looked like she needed a major caffeine boost, clutching a large coffee in one hand as she left her taxi.

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Fresh-faced: Sienna Miller showed little sign of her big night out when she stepped out bright and early on Thursday morning, arriving at the Global Radio studios in London

Sienna wowed in a pair of dusty pink, high-waisted trousers with a chic material belt.

The blonde beauty dressed the look down with a simple black top and a pair of stylish peep-toe heels.

The screen star wore her locks down loose and accessorised with large silver hoops earrings.

Think pink: She wowed in a pair of dusty pink, high-waisted trousers with a chic material belt

Extra height: The blonde beauty dressed the look down with a simple black top and a pair of stylish peep-toe heels

Super chic: The screen star wore her locks down loose and accessorised with large silver hoops earrings

Sienna proved just how close the steamy scenes placed her with co-star and director Ben Affleck at the London premiere of the film on Wednesday - where the duo got super cosy on the star-studded red carpet.

The actress looked sensational in a silky slip dress yet the blistering chill descending on the capital grew too much so the Hollywood hunk wrapped his coat around her before partying on into the wee hours.

Sienna dazzled in her chic monochrome gown with thin spaghetti straps and a delicate silk material, yet the six degree temperature led her into her co-star's arms. 

Always a gentleman: Sienna proved just how close she was to co-star and director Ben Affleck at the London premiere of the film on Wednesday

Good sports: The 35-year-old actress, who plays Irish minx Emma Gould, looked sensational in a silky slip dress yet the blistering chill descending on the capital grew too much so the Hollywood hunk wrapped his coat around her

Just days before at the LA premiere the duo were seen getting close and they made no exception on Wednesday as Ben wrapped an arm around her.

Strutting along the red carpet the duo greeted the world's press as a unit, before whispering to one another while they posed for the masses of cameras.  

Ben plays Joe Coughlin in the movie, the son of a Boston policeman, who falls in love with Sienna's character, Emma Gould, the mistress of the Robert Glenister's character, Albert White, who is the boss of an Irish gang of Boston.

What's so funny? Ben sported a shocked expression while Sienna stared humorously at his ensemble 

Good pal: Ben did his best to keep the blonde bombshell warm 

Hanging out: The two co-stars put on a fun-spirited display as they posed together on the red carpet - despite the chilly British weather

Dream team: The good pals were in good spirits as they put on a very cosy display on the red carpet

Leading man and his lady: All eyes were on the acting duo as the stepped out in style for the event 

No action-packed movie would be complete without a romantic story laden with sex scenes - and Sienna admitted the duo were forced into a bevy of romantic scenes - some of which left her in unprofessional fits of laughter.  

Speaking to E!, Sienna revealed: 'Ben and I are like brother and sister, thank God, so there was no awkwardness. There was just a lot of stupid giggling. He's very professional—I am not, but he is. 

'In that environment it was a cool scene. There was a montage in the script saying we did it everywhere: in the car, in the bar...I was like: "That's an entire day of just love scenes! OK. How do we do this?"

Up close: Sienna recently admitted their whopping nine hours of sex scenes tickled her

The object of his desire: The handsome star plays Joe Coughlin in the movie, the son of a Boston policeman, who falls in love with Sienna's character, Emma, who is the mistress of the Robert Glenister's character, Albert White , who is the boss of an Irish gang of Boston

Screen siren: Sienna Miller, 35, commanded attention as she made a glamorous arrival for the Live By Night's premiere at London's BFI Southbank on Tuesday night

Rock on! Sienna and Ben seemed determined to let the party live on as they headed to the Chiltern Firehouse restaurant in Marylebone shortly after

'Obviously, by the time nine hours of it has gone past, I was shaking with tears running down my face. I mean, I can't tell you—but you have to laugh. Ben is just professional. It is what it is.' 

Sienna's slinky satin number, which was mostly white with a diagonal slot of black, contoured her slim figure to perfection and bared her toned arms.

Opting for a vintage vibe, the British beauty's garment featured a black corsage on the left side of her chest. 

Famed for her sensational sense of style, Sienna's dress ticked all the red carpet boxes as she posed and preened while preparing to launch the movie. 

Hollywood hunk: Joining Sienna on the red carpet was her hunky co-star, Ben Affleck 

Glamour: The actress, who plays Irish minx Emma Gould, absolutely oozed elegance in a figure-hugging monochrome dress

Monochrome magic: The slinky satin number, which was mostly white with a diagonal slot of black, contoured her slim figure to perfection and bared her toned arms

Slinky: The garment hugged her trim midriff and pert derriere

Her glossy blonde locks were styled in old school Hollywood waves and were pinned back on one side, framing her striking features - which were accentuated in a glamorous coat of make-up.

Her towering open-toe heels boosted her height as she worked her angles on the red carpet while holding on to a chic, black clutch with one silver-encrusted hand. 

Taking her time as she posed for photographers and mingled with fans, Sienna was clearly in good spirits for the occasion.  

Vintage vibe: Her glossy blonde locks were styled in old school Hollywood waves and were pinned back on one side

Like a pro! There was a moment when she was all alone, soaking up the attention from the photographers 

Nice touch: Opting for a vintage vibe, the British beauty's garment featured a black corsage on the left side of her chest

Stunner: Her eyes featured a generous dose of mascara, while her lips sported pink gloss 

Standing tall: Her towering open-toe heels boosted her height as she worked her angles on the red carpet

Dripping in diamonds: Sienna couldn't resist flashing her stunning silver earrings as she posed over her shoulder 

Eternal beauty: Her stunning features were difficult to miss 

Ben meanwhile looked typically dashing in a fitted three-piece navy suit with showed off his muscular frame. 

The handsome star was wise enough to prepared for the cold in his slick coat yet was forced to share with slinky Sienna. 

He teamed the look with a light blue shirt, navy tie and brown shoes - while also sporting grey scruff.  

Star: Sienna braved the chill to sign autographs for fans 

Say cheese! She ensured to pose for photographs as well 

Dapper: Ben meanwhile looked typically dashing in a fitted three-piece navy suit with showed off his muscular frame

Stylish: He teamed the look with a light blue shirt, navy tie and brown shoes

Fifty shades of grey: The father of three also sported grey scruff 

Pleasing them: He took time out to sign autographs for eager fans 

Wrapping up: At one point it seemed like the weather was becoming too much for Sienna to handle 

The squad: Sienna and Ben posed alongside their co-stars, Robert Glenister (L) and Chris Messina (R) 

They're all there! All the stars squeezed in together for a group shot 

Popular lady: Sienna also got cosy with her other co-star, Chris Messina 

Also stepping out in style for the premiere was Made in Chelsea star Stephanie Pratt, who kept it super flirty in a heavily patterned co-ord set which flashed a peek of her toned stomach and flaunted her long legs. 

Model Jada Sezer showed off her curvaceous figure in a skin-tight black dress which flaunted her sensational pins. 

Actor Chris Messina put on a stylish display as he arrived with his gorgeous wife Jennifer Todd, who was clad in a stunning midi-length number.  

Talented man: As well as acting in it, Ben has also directed the flick 

'There was a lot of stupid giggling': Speaking to E! News, Sienna revealed they resorted to humour to get them through the hours of sex scenes

Details: Sienna ensured to harbour all of her essentials in a chic black and red rimmed clutch

Glam arrival: Also stepping out in style for the premiere was Made in Chelsea star Stephanie Pratt, who kept it super flirty in a heavily patterned co-ord set which flaunted her long legs

Gorgeous: The reality star accentuated her blue eyes with a heavy dose of mascara, which she teamed with a glossy pink pout 

Enviable frame: Model Jada Sezer showed off her curvaceous figure in a skin-tight black dress which flaunted her sensational pins

Elegant: Sienna's former step-mother, interior designer Kelly Hoppen, looked incredible in a sophisticated jade green velvet one-sleeved jumpsuit as she turned out to support the star 

Perfect pair: Chris Messina put on a stylish display as he arrival with his gorgeous wife Jennifer Todd who was clad in a stunning midi-length number

Spill the beans: The Scottish beauty was on hand to interview Ben for his role in the gangster flick, which is currently in cinemas

Tell us more: Jenni also had a giggly chat with Sienna, who was presumably spilling more sexy behind the scenes secrets with Ben 

Sienna and Ben seemed determined to let the party live on as they headed to the Chiltern Firehouse restaurant in Marylebone shortly after. 

The blonde beauty had dealt with the cold by pulling on a slightly mismatched navy coat atop her gown.

Ben meanwhile remained in his ruggedly handsome ensemble as he prepared to indulge in the delights of the London night life.  

Meal: Later in the evening, Sienna was seen departing a post-premiere meal at 34 Restaurant

So happy: The actress appeared to be in particularly jovial spirits as she made her exit

Maintaining the glam: The screen star still looked just as glam as when she hit the red carpet

A helping hand: The actress was guided through a group of handlers as she made her way out 

Layered: She threw on a smart blue jacket in an effort to stave off the biting wintry chill

Celebrate! Her co-star Ben was also seen leaving the same eatery after their celebratory night

Sign of the times: The Hollywood actor briefly paused outside to sign an autograph for a fan

Show me the way to go home: He quickly made his way to a waiting chauffeur-driven car

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