Mystery surrounds the death of the former husband of Russian spy Anna Chapman after he died from a multiple drug overdose, MailOnline can reveal.

Family members had insisted the death of Alex Chapman at the premature age of 36 was due to natural causes.

But his death certificate lists his cause of death as a multiple drug overdose with a coroner ruling his death as drug related.

Chapman was divorced from the woman dubbed 'Russia's most glamorous spy' when he was found dead at a house in Southampton in May 2015.

His ex-wife had been part of a one of the biggest Soviet spy rings ever uncovered while living in New York.

She was sent back to Moscow in 2010 as part of a spy exchange that saw double agent Sergei Skripal jailed for spying for MI5 and relocated to the UK.

Family members insisted the death of Alex Chapman (pictured on his wedding day to wife Anna) at the premature age of 36 was due to natural causes. But his death certificate says the Brit died as a multiple drug overdose with a coroner ruling his death as drug related

Alex Chapman (pictured left) was divorced from his wife Anna (pictured right) dubbed 'Russia's most glamorous spy' when he was found dead at a house in Southampton in May 2015

The 66-year-old is now in a critical condition in a Salisbury hospital after being deliberately poisoned by Russian agents acting on the orders of the Kremlin.

Members of Chapman's family had insisted to MailOnline that there was nothing 'suspicious' about his death two years ago.

A family member said: 'It was very distressing at the time, but he died from natural causes.

'There was nothing suspicious about his death. His father dealt with everything and it was very sad but I don't want to go into any further details.'

While his father Kevin confirmed his son's death he refused to divulge any further details.

It is thought family members did not want to reveal the drug overdose for fear his death could be linked to many other suspicious deaths of those who have spoken out against Russian President Vladimir Putin.

Chapman caused his ex-wife huge embarrassment after revealing details of their sex life following her arrest.

The former spy, who has forged a new career as a TV presenter and entrepreneur, is said to be a favourite of Putin and visited him at his country home.

In multiple interviews Anna made no mention of drugs playing any part in their four year marriage.

An inquest into Chapman's death was held on September 14th by the Coroner for Southampton and the New Forest.

Anna Chapman (pictured with ex-husband Alex) was sent back to Moscow in 2010 as part of a spy exchange that saw double agent Sergei Skripal jailed for spying for MI5 and relocated to the UK

The cause of death is listed as 'Multiple Drug Overdose' with the Coroner's conclusion that his death was drug related.

Chapman was found dead at a house near Southampton University although according to public records he was not listed as living at the property.

His last known address was in Bournemouth where he shared a house with three other people.

A former flat mate contacted by MailOnline refused to comment.

Former public schoolboy found himself at the centre of biggest spy scandal for decades when it was revealed his flame haired ex-wife had been tasked with seducing power brokers in the US capital Washington DC.

Alex told how during the first few months of their whirlwind romance, he saw Anna in both London and Moscow.

He told how he joined the mile high club with her during a BA flight back to Moscow in January 2002.

Sergei and Yulia Skripal (pictured) are still fighting for their lives after being attacked with a nerve agent in Salisbury, Wiltshire this month

Crime scene: Forensic investigators are still scouring Salisbury from top to bottom in search of the key to what happened to the Skripals

He said: 'When we were on the plane we came up with a plan to join the mile high club.

'I went to the toilet first and told her to follow later and knock. 'Anya was wearing a denim dress so I hitched it up and we just went for it.

'It was fantastic because of the thrill of doing it on a plane. We were in the toilet for about 15 minutes and then one of the cabin crew knocked on the door.

'I said Anya had been sick and I was helping her.'

Alex then produced a picture of Anna wielding a whip and another toy and wearing nipple clamps.

'I found her Russian accent such a turn-on, he said. 'She was the most beautiful person I had ever met, with an extraordinary body, and I was infatuated with her.'

The couple had met in 2001 at a rave in London while Anna was still a student and Alex described her as the most beautiful woman he had ever met.

They were married in Moscow in 2002 after a whirlwind romance and Alex discovered her father Vasily Kushchenko was a former senior KGB agent.

Chapman's ex-wife Anna (pictured) had been part of a one of the biggest Soviet spy rings ever uncovered while living in New York

Chapman caused his ex-wife (pictured) huge embarrassment after revealing details of their sex life following her arrest

Alex wore an ill fitting dinner suit, all he could rent in Moscow.

There were no rings as they couldn't afford them, nor any guests.

A lonely witness confirmed the nuptials. Despite the bizarre circumstances, the marriage was a success for several passionate years.

In 2010, Chapman was part of a Cold War-style swap with Skripal Alex said his wife changed during their four-year marriage and began to mix in different circles with wealthy Russians.

'She fell in with a group of people who had a lot of influence. She would go to film premieres and became arrogant and obnoxious, always going on about powerful people,' he said in a 2010 interview with The Daily Telegraph.

Of her marriage to Alex, Anna said in 2011: 'My marriage to Alex was based purely on mutual love, and I still remember the days we spent together with real tenderness and nostalgia.

'I ask you not to look for ~secret motives~ where there aren't any.

'My love story with Alex was one of them. It was love at first sight, which only grew stronger every day.

Pictured: Anna Chapman, who was sent back to Moscow in exchange for former double agent Sergei Skripal

'We married secretly in Moscow, and it was very romantic.

'Our parents knew nothing about our relationship and plans, and most likely they would not have approved the marriage, though later I was close to Alex's mother and father.

'I had on my school graduation dress - I only wore it three times, my big day at school, the day I met Alex, and when we married.'

Anna went on: 'Alex is very sensitive, he felt music like no-one I met before, he could draw any picture as if he had studied art all his life.

'He somehow sensed people on a different level to other men.

'He put his soul into every action. He found strength when things went really wrong, when everything around him totally fell apart, he began his life from scratch again and again.

'Alex is an incredible, talented person, who still hasn't yet found himself in this life but I have faith things will become better and he will find his happiness because he does know how to love and care for a woman.

Russia's most glamorous spy: Anna Chapman is pictured on a beach photo shoot

'He had such a tenderness in his touch, his looks, his words. When you truly love someone, you become one. This was how we were. We could not make decisions without each other.'

With a smile enveloping her face, she added: 'Everything linked to Alex was soaked with true English culture, it's unbelievable.

'It was so natural and beautiful to fall in love with someone representing something I was so curious about. It took me precisely one minute to fall madly in love with him.

'Every time he opened his mouth, I enjoyed his beautiful manner of speaking, I was captivated by his accent.

'Whenever he rolled his tobacco in his loose-hanging jeans with his Clark's shoe and Liam Gallagher - style hair, it took my breath away.

'His manly beauty, I would even say his aristocratic beauty, seemed simply ideal to me.

'I had neither the strength, nor desire to fight this beautiful feeling, which opened up whole new fairy tale world for me.

'Yet if everything was so good why did the marriage fall apart after qualifying for a UK passport? '

Alas, everything beautiful comes to an end at some point, and there is always a new stage and better road to start walking on,' she said, also declining to answer any questions of her alleged spying either in the US or Britain.

'My time in Britain has made me better in so many ways that it's hard to tell what I would be if it wasn't for London.

'It was certainly my honour to be part of this nation, even though for a short while.'

She is, however, furious over her nude pictures taken by Chapman and also by an earlier British lover Marcus Read being made public.

Explicit pictures taken by one-time disc-jockey Read, 38, recently appeared in Playboy.

'I don't know whether he was forced by someone to do this, or was paid for it,' she said.

'I don't want to blame anyone before I know that. Frankly speaking, I don't think I want to go into finding out.

'But it's clear whoever organised this has definitely achieved his goal.

'It made me so miserable, it actually made me cry for the first time in a very long period. So, congratulations, you have done it.'

Pictured: Former wife of Alex Chapman, Anna, poses with a gun

She was 'shocked and horrified' when told by her New York lawyer that shots taken by Mr Chapman had been published while she was scared and traumatised inside a US prison, she said.

'Don't you think it's enough for one person to be embarrassed so much?,' she asks, shaking her head.

'After everything I have been through in recent months, the pictures in Playboy were like the final blow that really hit me badly. It made me really down and miserable.

'It keeps on damaging my reputation in such a bad way.'

After they split Anna relocated to New York where with the aid of a $1m cash injection from the Russian Government set up an internet property business.

But according to the FBI the business was a front for her spying activities and she was part of a group known as the Illegal's Programme.

As a 'sleeper agent' it was her job to infiltrate power circles in the US capital Washington DC and report back to her Kremlin paymasters.

Dubbed Russia's 'most glamorous secret agent', she (pictured) was one of ten Russian spies exchanged for Skripal in July 2010 in Vienna

The ex-spy now runs an antique shop in a trendy district of Moscow and works as a TV host Anna was arrested in 2010 along with nine other agents who had settled into seemingly ordinary lives in America.

She pleaded guilty to charge of conspiracy to act as an agent of a foreign government.

Dubbed Russia's 'most glamorous secret agent', she was one of ten Russian spies exchanged for Skripal in July 2010 in Vienna.

While she capitalized on her fame - posing in stockings and suspenders for Maxim magazine - Skirpal began a new life in the market town of Salisbury, Wiltshire.

Her ex-husband said he had lost contact with his wife, but being exposed as a female James Bond did not come as any surprise.

He said: 'Whether or not she's a spy, who can say, but when I read about her being arrested it wasn't that much of a surprise to be honest.

'It made sense because of all her erratic behaviour, all these high society people she was going on about. When I told my mother she said 'I knew it!'.'

Mr Chapman added in 2010: 'I don't think she was working as a spy here but I suspect she had been conditioned towards that end.'