They played the roles of two down and out heroin addicts in Trainspotting twenty years ago.

But Ewan McGregor and Jonny Lee Miller's characters Mark 'Rent Boy' Renton and Simon 'Sick Boy' Williamson looked to have kicked their habits and adopted a professional demeanour as they shot scenes for the highly-anticipated sequel on Saturday.

The actors were were joined by director Danny Boyle, 59, and the crew outside the Scottish Parliament Building in Edinburgh as the sun shone down.

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Hard at work: Ewan McGregor and Jonny Lee Miller shot scenes for the highly-anticipated Trainspotting sequel in Edinburgh on Saturday

The pair were business-like in appearance, with Ewan wearing a khaki coat over a black suit as he carried a bundle of paperwork.

Meanwhile, Jonny, 43, wore a grey suit with a black shirt and tie and carried a black laptop case in his right hand.

The stars' faces held serious expressions, no doubt they were heading to the government building for matters of importance.

Three amigos: The actors were were joined by director Danny Boyle, 59, and the crew outside the Scottish Parliament Building in Edinburgh as the sun shone down

Twenty years later... The pair were business-like in appearance, with Ewan wearing a khaki coat over a black suit as he carried a bundle of paperwork

Suited and booted: Jonny, 43, wore a grey suit with a black shirt and tie and carried a black laptop case in his right hand

Jonny and Ewan came face to face in the square, before heading side by side towards the government building. Jonny's peroxide locks shone in the light while Ewan sported a short back and sides.

In between takes the duo spoke with award-winning Boyle who tried to pass on his vision for the scene.

Onlookers couldn't help but trying to capture the actors at work as they watched on from a distance and took pictures with their cameras.

Stand off: Jonny and Ewan came face to face in the square, before heading side by side towards the government building

Job done: The pair had mischievous looks on their faces as they exited the building

Through gritted teeth: Jonny's peroxide locks shone in the light while he wore a pained expression on his face

All together now: Jonny and Ewan posed for a fun selfie together in their matching baker boy caps

The new film is based based on novelist Welsh's follow-up book, Porno, which is being adapted by screenwriter John Hodge for the big screen.

The sequel is set ten years after Trainspotting and sees the characters cross paths again, but with an alternative gritty backdrop of the pornography business, rather than heroin use.

In Porno, Renton owns a nightclub in Amsterdam, Begbie is being released from prison, and Spud is actually trying to kick his drug habit.

Spud also has love woes as his relationship with his partner Alison is strained and he feels like he has become a burden on her.

Creator Welsh is set to appear in the role of Mikey Forrester in the follow-up.