The face and the voice of the 78-year-old man being filmed on a mobile phone on a flight from Nepal to France were eerily familiar.

However, it was his quiet, resolute statement that he had “a lot of people to sue – including the state of Nepal” which was for me even more recognisable.

At first this seems to be the declaration of a man falsely accused, wrongly punished and who was therefore going to exact his revenge, but it was characteristic of what I remembered him saying to me several years previously in the oddest interview I have ever conducted.

The man being filmed was Charles Sobhraj, a serial killer also known as “The Serpent”, who had just been released from jail in Kathmandu, having spent 19 years in custody for the murder of an American woman called Connie Jo Bronzich and her Canadian friend Laurent Carriere.

Late in December last year Nepal’s Supreme Court ordered Sobhraj’s deportation back to France, after he had served more than three-quarters of his sentence, and at a time of his declining health and the fact that he had been well-behaved whilst in custody.

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Sobhraj has been linked to more than 20 murders between 1972 and 1982 – mostly of young Western tourists on the “hippy trail”, who were drugged, strangled, and sometimes burned. Prior to his Nepalese sentence he had already served two decades in prison in India.

He escaped from one Indian jail, but was recaptured and later claimed that the escape had been engineered so as to create the circumstances that would mean that his sentence was extended. This would allow him to avoid extradition to Thailand, where he was wanted on more murder charges. Those charges were indeed soon dropped due to the Thai statute of limitations.

So in 1997, after completing this Indian sentence, Sobhraj was deported back to France, where he was to stay for the next six years – often giving interviews in his Parisian flat to various criminologists and journalists. However, over time the interview requests stopped, and Sobhraj seemed destined to live out the rest of his life anonymously, and in circumstances very different to those portrayed in the BBC series The Serpent.

Then in 2003 he left Paris and returned to Nepal – the only country in the world where there was an outstanding warrant for his arrest. Unsurprisingly, he was eventually detained in Kathmandu, having been spotted several times gambling in one of the Nepalese capital’s casinos.

HeraldScotland: Nepalese police escort Charles Sobhraj to the immigration office in KathmanduNepalese police escort Charles Sobhraj to the immigration office in Kathmandu (Image: Newsquest)

Now you might be thinking, why would he go back to the one place where he might get arrested having fought so hard to get released from jail?

It’s a good question, and made all the more relevant when it becomes clear that Sobhraj wasn’t arrested immediately on flying into Nepal, but only after several nights of gambling in the same place, and in response to his picture appearing in the local newspaper. So, you might also be thinking, did he want to be caught?

I think that he did, but not because he was remorseful about what he had done to Connie or Laurent. I think that he was simply trying to reinvent his “brand”; attempting to remind the world that he was a serial killer; and desperately hoping to hang on to his infamy and notoriety.

Like the gambler that he has always been, he was rolling the dice one more time in the arrogant belief that he could outwit the Nepalese authorities – who were indeed slow to make their arrest – and in doing so remind us all what a clever, cunning, super predator he was.

In 2018 I went to Kathmandu to put that analysis to him, although to be honest I didn’t expect him to answer truthfully, even if he claimed he was “delighted” that I was coming, and keen to “get to know me”.

Serial killers that I have interviewed fall into two distinct types: the silent, who never discuss their crimes; and, secondly, those who speak endlessly about what they did, but not necessarily with any insight, or indeed honesty.

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In my experience this latter type of serial killer obfuscates and dissembles, and rarely offers a straight answer even to the simplest of questions. We may have spoken and then corresponded at length, but Dennis Nilsen, for example, never really offered answers to the questions that I put to him.

Instead he found ever more creative ways of confusing and muddling his replies to the extent that I could never be certain if he had, or had not, eaten the flesh of his victims, or whether he had engaged in necrophilia.

In the end, for various reasons, I concluded that he had done both, but it suited Nilsen not to be clear, and to deliberately offer answers that were equivocal and imprecise.

Sobhraj was the same, and my time in Kathmandu was a frustrating game of state politics – was I going to be allowed entry to the jail where he was being held to interview him, endless meetings with officials and so-called fixers, and even with Sobhraj’s heart surgeon who wanted to offer me his own understanding of his patient.

However, when I eventually did speak with Sobhraj he taught me one thing that I hadn’t until then really appreciated – serial killers are very conscious of what gets reported about them, and how they are portrayed.

They don’t just want to be discussed – which makes them believe that they remain relevant – they also want to control the contents of that discussion, and therefore how we might view them.

So of course Sobhraj wants to sue the Nepalese government as it’s one the last things that he can do to ensure that he generates even more column inches, but more than that it gives him a chance to present himself as a victim.

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He never said this to me directly, but I remember vividly something that he did offer in one of his Parisian interviews. Most people get out of the kitchen when it’s too hot, but not Sobhraj – “that’s when I go into the kitchen”.

Risk-taking behaviour of this kind is of course a classic example of psychopathy, but let's not go there just in case he wants to sue The Herald too.

Emeritus Professor David Wilson. His new Channel 4 series In the Footsteps of Killers is on Channel 4 on Thursdays at 9pm.