Porter, 39, wants to say he won't spend it on heroin but he 'probably' will

A business analyst who earns $100,000-a-year is hiding a chronic heroin addiction from his boss and colleagues.

Seth Porter*, 39, spends his days working at a leading Australian trading company - crunching numbers and advising senior management on business strategy - as well as managing a heroin habit he has had for 20 years.

Mr Porter, from an Australian city, injects himself at least once a day and started using the highly addictive opiate at just 19 after experimenting with other drugs.

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Dr Mark Daglish, who is the director of addiction psychiatry at Royal Brisbane Hospital, said it was rare to come across a high-functioning drug addict

Seth Porter*, 39, spends his days working at a leading trading company - crunching numbers and advising senior management on business strategy - but hides a heroin addiction from his colleagues

'I didn't think about addiction or overdose when I first used. I had taken other drugs in the past like speed, ecstasy and acid. I was always taught that they were addictive and dangerous and I found that to be a lie,' he told Daily Mail Australia.

'So when a friend encouraged me to try heroin I didn't really think twice. But I obviously found out that this was the drug that was incredibly addictive.'

Mr Porter has been using since he was 19 years old and has always managed to maintain his professional life.

But his drug habit almost claimed his life in the early years of his addiction.

'I've overdosed once, it was very early on – I would have been 19 or 20,' Mr Porter said.

'I just remember using and then the next thing I knew I had paramedics over me with a resuscitation machine.

'The person I was with had called an ambulance. I don't know if I would have died or not if my friend hadn't called them.'

The addict (pictured above using heroin) claims he has never been unemployed for long periods and he has never been sacked or made redundant

Mr Porter said his addiction did not stop him from doing his job. He has been using heroin since he was just 19

Despite the near-death experience, Mr Porter took heroin again two days later.

'I've been addicted since I was 19 but I've always managed to be pretty successful professionally,' Mr Porter told Daily Mail Australia.

'I live between worlds and I can navigate that distance.

'I've done it for 20 years - I somehow manage to function. I'm just a normal person who happens to have a massive weakness in heroin.

'I don't want to glorify heroin, I would be a much better person without it. It's not like I'm saying: "Hey look at me, I'm a junkie and I can work a decent full-time job".

'I despise being an addict. It's like a voice in the back of your head that won't leave you alone. It doesn't go away, it won't stop.'

Dr Mark Daglish, who is the director of addiction psychiatry at Royal Brisbane Hospital, said it was rare to come across a high-functioning drug addict.

'We almost never see people like this in our clinics in the public sector. We do see the ones who try to be functioning and fail, and the ones who get caught,' Dr Daglish said.

But Mr Porter has defied the odds.

The addict claims he has never been unemployed for long periods and he has never been sacked or made redundant.

In fact, he is considered so important to his employer that he will be given a large Christmas bonus this year because he is 'so valuable to the company'

In fact, he is considered so important to his employer that he will be given a big Christmas bonus this year because he is 'so valuable to the company'.

'I'd like to say I won't spend the whole bonus on heroin, but I probably will,' Mr Porter said.

Incredibly Mr Porter sometimes sneaks off to the toilets at work and uses.

'Occasionally I have used at work. I try not to, but it does happen. Thank god for floor-to-ceiling locked doors,' he said.

'It's amazing how I have gotten away with being high at work for such a long time.'

But Mr Porter was nearly caught out earlier this year.

He was in a two-hour meeting and had used heavily that morning.

'By the end of the meeting I was coming down – when you're coming down really hard from heroin it's almost impossible to keep your eyes open. I nodded off and my boss noticed,' Mr Porter said.

'I blamed it on chronic migraines and my boss bought it. He told me to take two days off – with pay. So I went home and used.'

Mr Porter does not know how he manages to function with such a deep addiction when so many others fail.

A track mark from the needle he used to inject heroin. Last year he was almost caught out by his boss

Porter keeps his drug paraphernalia hidden in an everyday glasses case

'But what separates me from the typical addict is I genuinely enjoy working,' he said.

'It helps that I look the part - I dress well, I wear reading glasses and I have a good vocabulary.

'I also have a genuine interest in things like business and politics. I think that has always helped me speak well in interviews and come across as somebody you would want to hire.

'I have always been able to convince people that I am smarter than I am.

'The constant fear I have is that when you come across genuinely brilliant people, they don't buy my nonsense for a second, they see straight through it.

'Thankfully those people are few and far between in the upper-middle management levels of Australian business.'