In 2008, 23-year-old Norwegian student Martina Vick Magnussen was killed in an apartment near Mayfair.

Hours after her death, the only suspect in the case fled the UK to Yemen.

He's never been questioned by the police.

I'm Noel El-Makafi and I made a promise to Martina's family 15 years ago to find out what happened.

Murder and Mayfair is the new mini-series right here in the documentary.

All episodes are available now.

Hello, I'm James Reynolds. Welcome to the documentary from the BBC World Service.

In OS conversations, we bring people together from around the world to discuss how major events affect their lives.

This time, it's conversations on fentanyl in the United States.

The other month, a drug enforcement official in the country described it as the single deadliest drug threat the US has ever encountered

to parents share their experiences of losing someone to fentanyl.

And we bring together three medical professionals who deal with overdoses almost every day.

Patients that are breathing at a very slow rate, sometimes no respiratory effort at all.

And these are patients that we aggressively ventilate and then we administer Narcan to get these patients back to their normal respiratory drive.

Fentanyl has been around since the 1960s and small doses are used safely every day by medics for pain relief.

But as an illegal drug, fentanyl is blamed for more than 70,000 deaths in the US every year.

And from people in the streets right up to the president, there is recognition that America has a real problem.

One of the things to understand is that fentanyl is 50 times more powerful than heroin.

Just two milligrams of fentanyl could kill you and that amount could fit on the tip of a pencil.

You may have seen celebrity deaths link to it, but as the numbers suggest the drug touches so many regular lives as well.

And that's what we've been hearing about.

Before I go any further, I should say as you might expect that our conversations contain themes of trauma and drug use.

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