Did you spot this Harry Potter star in the BBC's The Responder?

The drama stars Martin Freeman, MyAnna Buring and more

BBC's new series The Responder impressed viewers with debut episode on Monday night and many will be tuning into episode two on Tuesday night.

MORE: Meet The Responder actress Elizabeth Berrington

The police drama stars and actor Martin Freeman as Chris Carson – a night shift responder officer who's struggling with the pressure of his work and family life. Other actors listed in the credits MyAnna Buring, Adelayo Adedayo and Warren Brown. But did you know a star appears in the cast, too? Get all the details here...

WATCH: BBC's The Responder official trailer 

Actor Ian Hart plays the part of Carl in – a notorious drug dealer in the Liverpool area who is constantly avoiding the law. However, things are complicated by the fact that first responder Chris has a historical connection with Ian due to them having gone to school together.

Viewers may recognise Ian, who has appeared in plenty of TV shows and films over the years, from his stint in and the Philosopher's Stone back in 2001. The actor played Professor Quirrell in the first film of the fantasy franchise.

Since then, Ian has gone to land credits in more titles such as , Netflix's and, more recently, on BBC as Ryan McGregor. And Ian isn't the only cast member to appear in

MORE: The Responder: viewers spot plot hole in episode one

MORE: Meet the cast of BBC's The Responder

Ian Hart plays Carl in The Responder

David Bradley takes on the role of Davey – a homeless man living in Liverpool City Centre. Davey and Chris became friends thanks to Chris' night shifts crossing their paths. David Bradley played Mr Filch in the series and more recently appeared in Ricky Gervais'

The full synopsis for reads: "Whilst trying to keep his head above water both personally and professionally, Chris is forced to take on a new rookie partner Rachel. Both soon discover that survival in this high pressure, relentless, night-time world will depend on them either helping or destroying each other."

Did you recognise Ian Hart?

It seems episode one was well received by audiences, however some did notice a minor plot hole. Taking to social media, one person said: "Why is this copper doing emergency response shifts on his own? I love Martin Freeman and I love police dramas but they need to be at least slightly credible."

A second wrote: "Why is he on duty on his own? I thought they work in pairs? Have I missed something???" Meanwhile, a third tweeted: "Great actor. Not sure why he's allowed out on his own with his issues, but hey ho, no story otherwise…"

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