LINE of Duty star Martin Compston has declared his support for the SNP and urged Scots to back Nicola Sturgeon in the ballot on Thursday.

He made the plea shortly before the Line of Duty finale, at an event attended by other high-profile SNP supporters - including Alan Cumming, Brian Cox, Val McDermid, and Stuart Braithwaite.

Compston, 36, is a strong proponent of Scottish independence and has described the prospect of freedom from the UK as feeling like “walking on air”.

The Greenock-born Scots star has supported independence from a young age and hopes for a second referendum.

Compston explained: “Everyone is allowed an opinion. Whether that be politicians down south or some lovely incredible entertainers who have moved abroad for whatever reason.

READ MORE: Martin Compston has the perfect response to Tory trolls after backing Yes

"Myself, I’ve lived across the world. That’s the beauty of free speech. Everyone is allowed an opinion. But what matters is votes.

"And it’s the people who live here, work here, and who vote here, whose gonna make the difference.”

He attributed his support for Scottish independence to a malfunctioning Westminster that doesn’t care about Scotland, the constitutional issue of Brexit, and the divisive matter of trident.

Compston continued: “Let’s be honest about this stuff, if we had a functioning Westminster that really cared about every region of the UK.

“That didn’t take parts of the UK out of Europe against its will.

“And the decisions, the big decisions, whether it be Scotland’s future relationship with Europe, whether it be nuclear weapons on the Clyde, are best taken by the people who live here.

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“And we can’t forever live in this perennial situation, where it’s just Tory government after Tory government at Westminster, who don’t care about Scotland.

“They just leave us in these miserable situations, which make us feel utterly powerless to deal with."

Compston insisted the only way to empower Scots is through the SNP.

He concluded: “We have to be in control of our own destiny. And the only way to do that is through an SNP or an independence majority at the Scottish Parliament.

“And then we take it from there.”

Here's the full transcript of Mhairi Black's interview with Martin Compston:

Mhairi Black: Hello, Martin. As you are here in a personal capacity, I'll remind you that you no longer reserve the right to be interviewed by someone at least one rank senior. At this moment in time, as you are well aware, there is great public interest surrounding a clandestine network of corrupt police officers working with organised crime.

So let's not waste time here son. Are you the fourth man known as 'H'?

Martin Compston: No comment.

Mhairi Black: Will you survive tonight's episode?

Martin Compston: No comment.

Mhairi Black: Moving on then, and this will not be the last reference to Line Duty here. But this evening we are interested in one thing and one thing only. So, can you tell us why this election is so important? 

Martin Compston: Well look, every election is important, of course. We’re coming out of something here, this pandemic, this crisis that none of us have faced before.

I think even people who don’t like Nicola Sturgeon, for whatever reason, have had to admit that she has been by far the most competent leader on these islands dealing with this crisis. And she’s the one I think is best placed to take us forward getting out of it. So, I do really think that we are in a situation now where we need the best people, the most competent people, in charge of Scotland. To make sure that we come out of this a better place than we went in.

Mhairi Black: What would your message be to voters at this election?

Martin Compston: Get out and vote. Everyone is allowed an opinion. Whether that be politicians down south or some lovely incredible entertainers who have moved abroad for whatever reason. Myself, I’ve lived across the world. That’s the beauty of free speech. Everyone is allowed an opinion. But what matters is votes. And it’s the the people who live here, work here, and who vote here, whose gonna make the difference.

And whether that be for this election or any other election moving forward or moving forward. Because let’s be honest about this stuff, if we had a functioning Westminster that really cared about every region of the UK. That didn’t take parts of the UK out of Europe against its will.

And the decisions, the big decisions, whether it be Scotland’s future relationship with Europe, whether it be nuclear weapons on the Clyde, are best taken by the people who live here.

And we can’t forever live in this perennial situation, where it’s just Tory government after Tory government at Westminster, who don’t care about Scotland. And they just leave us in these miserable situations, which make us feel utterly powerless to deal with. We have to be in control of our own destiny. And the only way to do that is through an SNP or an independence majority at the Scottish Parliament. And then we take it from there.

Mhairi Black: Excellent! No, thank you for joining us, Martin. I know your time is precious, and genuinely, I'm hooked on Line of Duty. I rewatched it from the start. So to keep things moving so that we can all watch the finale at 9pm tonight, I'll hand over to you. Thanks Alan [Cumming]

It comes as Line of Duty's penultimate episode contained a huge mistake about Scotland’s unique legal system.

Character Detective Inspector Steve Arnott – played by Greenock-born Martin Compston – mentioned a “Glasgow coroner” and “subsequent inquest”. However, there are no coroners in the Scottish legal system and no inquests.

In Scotland it is usually the Procurator Fiscal who has a similar but not identical role to the English coroner.

READ MORE: BBC's Line of Duty red-faced after glaring error about Scottish legal system

The Lord Advocate is technically in charge of investigating any death in Scotland which requires further explanation, but he or she usually assigns such an inquiry to the Scottish Fatalities Investigation Unit (SFIU). This is a specialist unit responsible for investigating all sudden, suspicious, accidental and unexplained deaths.

Back in 1996, Procurators Fiscal investigated all sudden deaths where the circumstances surrounding the death appeared suspicious, accidental or unexplained, and the police usually carried out the inquiry, normally after a post-mortem examination had been carried out.

The nearest Scottish equivalent to an inquest is a Fatal Accident Inquiry.

The mistake came when Acting DSU Joanne Davidson, played by Scots actress Kelly Macdonald, was being interviewed by Superintendent Ted Hastings, played by Adrian Dunbar, and DI Arnott following her arrest.

They were joined by Anna Maxwell Martin playing Detective Superintendent Patricia Carmichael.