The Black Swan review: This astounding BBC documentary about crooked lawyers knocked me for six – and I can see why it broke ratings records with its breathtaking final twist, says DEBORAH ROSS

You may not be very interested in what goes on in a lawyer’s office in Denmark. My interest was zero.

But the four-part documentary Black SwanIt’s gripping, astonishing television, set (secretly) in a (slanted) lawyer’s office in Copenhagen, and it knocked me over. (I think this is a cricket metaphor, but since I have no interest in cricket myself, I can’t say for sure.)

In Hamlet, Marcellus may have been referring to this spectacle when he tells Horatio that ‘something is rotten in the province of Denmark.’

Let’s get to the point. The main character is Amira Smajic, a Copenhagen-based lawyer who, after living a life of lies, crime and fraud for ten years.

He contacts investigative filmmaker Mads Brugger, saying he must expose this world and expose his clients; some of them are old-school criminals convicted of violence and even murder, while others come from the top of Danish society (lawyers, businessmen, partners in a large construction company).

Can these two worlds not be connected or can they be connected?

You may not be very interested in what goes on in a lawyer’s office in Denmark. I had no interest… But Black Swan, the four-part documentary set (secretly) in a (bent over) lawyer’s office in Copenhagen, is gripping, astonishing television

It was so explosive when it premiered in Denmark last year that it not only became one of the most watched programs in Danish TV history, but also led to several high-profile arrests and resignations.

Why Black Swan? Because the ancient Romans thought that black swans were not real and they described an event that no one could imagine.

Remember, Denmark boasts of being the least corrupt country in the world.

Smajic wearing her hair in such a high, tight ponytail must be painful – let her go!; Give your scalp a break! Ah! – says he came forward because he was tired of this life.

His expertise is money laundering and tax evasion, but he’s also your go-to guy if you want to dispose of toxic waste illegally.

He did a good job. At one point he had a Bentley and ‘I bought shoes like other people buy milk.’ But he says he can’t continue.

It was so explosive when it premiered in Denmark last year that it not only became one of the most watched programs in Danish TV history, but also led to several high-profile arrests and resignations.

‘If you ask me who I am today, I’m a poor person,’ he says.

‘I’m tired of lying. I’m tired of living a life where I have to size everyone up and be on guard. ‘I’m tired, I’m tired.’ Crying. Real tears?

All I will say is that there is a tremendous, breathtaking change in the last episode.

It’s a fascinating character study, even if there’s no secret to uncover.

Brugger arranges for him to meet with clients in an office with microphones and cameras hidden in electrical outlets.

There’s a heart-stopping moment when a visitor tries to charge someone’s phone, but Smajic remains unshaken.

The woman, known in the underworld as the Ice Queen for her cold-blooded attitude towards a wide variety of crimes, coldly directs him to an alternative.

He offers coffee and deftly betrays their trust.

Why Black Swan? Because the ancient Romans thought that black swans were not real and they described an event that no one could imagine.

Where to start? There is a top firm lawyer who is willing to overlook the “fake invoice mills” necessary for money laundering.

The partner of the construction company is trying to dispose of toxic waste illegally.

The man who will bury him in a field somewhere is Fasar, one of Smajic’s most regular visitors.

A known criminal with ties to an outlaw biker gang. At one point, he disappears to Pakistan for a while to kill a witness in an upcoming trial.

He asks her if she wants to watch him do it live.

A businessman who has an Instagram account that looks incredibly luxurious and shows off his love for Japanese food, caviar and champagne has multiple companies that turn black money into white.

He’s so right and self-satisfied that you find yourself yelling at the screen, ‘Gotcha!’, as he explains to Smajic with diagrams how his complex system works. You may find yourself shouting:

I can’t say that I warmed up to Brugger, who interviewed Smajic many times and seemed cold and arrogant, but this is a great pain.

As for Smajic, who came to Demark as a Bosnian child refugee, he is so illegible that even Brugger cannot get into his depths. What’s his game?

But in the final hour we get a hint of what he’s really up to, and it’s shocking.

This is a complicated show, and I don’t have space here to address ethical or moral concerns, the extent of police involvement, or what the consequences were.

Just watch because if it’s happening in Denmark, it’s happening everywhere.