Professor David Goodall has voluntarily ended his own life, after making his final preparations and saying goodbye to family.
The 104-year-old Australian scientist revealed his lively humour, and a hint of nervousness, with his poignant last words: "This is taking a long time."
Professor Goodall had long advocated for voluntary euthanasia but had to fly to Basel in Switzerland to proceed with the hotly-debated scheme, which is not legal in Australia.
"At my age, or less than my age, one wants to be free to choose the death when the death is at an appropriate time," Prof Goodall told reporters. "I no longer want to continue life.
"I'm happy to have a chance to end it."
At 12.30 today (10th May) Professor David Goodall, 104 years of age, died peacefully at Life Cycle, Basel, Switzerland from an infusion of Nembutal.
— Philip Nitschke (@philipnitschke) May 10, 2018
The top ecologist flew from his home in Perth last week, saying an emotional goodbye to much of his Australian family, including his grandchildren and great-grandchildren.
He had said he would rather have died at home in Australia.
The British-born professor spent some time in France visiting more family before arriving in Basel for his assisted voluntary death.
Prof Goodall spent his final day exploring the Basel University Botanical Gardens with three of his grandchildren, who said they were proud of his bravery and glad he would die on his own terms.
He enjoyed a last meal of fish and chips and cheesecake before Beethoven's Ninth Symphony, Ode to Joy, was played in his final moments.
The procedure was carried out by Eternal Spirit, a branch of the Swiss clinic Life Circle, which is committed to promoting the legalisation of voluntary euthanasia.
The clinic has helped 73 people voluntarily die in the past year.
In 2015, 967 people chose to end their life in Switzerland, one of the few countries where foreigners can opt to end their life.
Before the professor even arrived in Basel, he was required to submit an application to Life Circle detailing why he wanted to die. The 104-year-old then met with two Swiss doctors on two separate occasions to clarify if his decision to die met their guidelines.
He was also required to meet with a psychiatrist yesterday to determine he was of sound body and mind.
After being given the final OK by a Swiss doctor, the professor was able to book in for his own death.
Today, Prof Goodall would have signed a final form, again approving his wish to die.
On Thursday night (AEST), surrounded by four family members and a close friend, Mr Goodall first took a drug to prevent him from vomiting.
Most Swiss foundations ask patients to drink a lethal cocktail of medication, but because it burns when swallowed, Eternal Spirit instead administers the sedative through intravenous infusions.
A professional prepares the needle, but it is up to the patient to open the valve that allows the short-acting barbiturate to mix with a saline solution and begin flowing into their vein.
The professor would have been filmed while he took the drug, cited by Life Circle as "the only reliable evidence he or she has executed the application by themselves and in full awareness".
Within a few minutes of taking the drug, the 104-year-old fell asleep and he died within half an hour.
"He almost became a little impatient at the end, having to go through quite a few necessary formal steps that are part of the process," Philip Nitschke, founder of right-to-die group Exit International, told AAP. "During the paperwork, he said 'what are we waiting for?'
"His final words were 'this is taking a long time.'"
Prof Goodall was asked four questions to confirm he was still lucid and knew what he was about to do, the final being "What is going to happen when you press the button?"
The professor reportedly replied: "Well, I hope my heart stops."
Dr Nitschke said Prof Goodall's death was peaceful. "I think he was very clear what he was doing.
"It was rather sad but eventually he got what he had wanted for quite a while at the end of a long life."
After his death, Mr Goodall's friend were asked to call the police and report an extraordinary death — a requirement of Swiss law.
The authorities then release Goodall's body to the family and a funeral service will be held.
He is expected to be cremated in Switzerland, with his ashes remaining in the country, while his family in Perth will hold a memorial in the next few months.
Prof Goodall lived alone in a Perth apartment, and had stepped down from full-time employment in 1979. He continued to work, however, editing a 30-volume book series called Ecosystems of the World in recent years, and was awarded the Order of Australia for his contributions to science aged 101.
In 2016, aged 102, he won a battle to keep working on campus at Perth's Edith Cowan University as an unpaid honorary research associate.
The professor's quality of life had deteriorated over the past few years and the 104-year-old attempted to take his own life at least three times before deciding to get professional help.
In a final press conference on Wednesday, Prof Goodall was asked by reporters if he had a song in mind for his final moments. He sang them a few bars from Beethoven's Ninth Symphony in response.
The renowned botanist said he was surprised by the level of interest in his case, but pleased to have the opportunity to advocate for assisted dying.
"I feel very privileged that I will be able to be there when my grandfather passes away," Mr Goodall's 30-year-old grandson Daniel told the Daily Mail.
"He is so brave and I am so glad that he has been able to make his own choice.
"It is his wish that he can end his life, but such a shame that he was not allowed to do it in his own country," he said.
Another of the botanist's grandchildren, Duncan, 36, also told the publication he would be by his grandfather's side when he passes away.
"I think what he is doing is incredibly brave. My grandfather has approached this in a completely rational way and not let any emotion get in the way.
"He wants to die and he wants to die on his own terms. The fact that he is doing this so publicly shows how brave he is," he said.
Victoria is the only state or territory to have legalised voluntary euthanasia in Australia.
The legislation was passed after a heated three-day debate in parliament that ended with politicians making the scheme available only to terminally ill Victorians with less than six months to live.
Switzerland has allowed assisted suicide since 1942.
Despite the passing of the bill, the law won't come into effect in Victoria until the middle of 2019.
Pro-life organisation Cherish Life Queensland issued a statement saying Prof Goodall's actions would encourage vulnerable people to follow his example.
Readers seeking support and information about suicide prevention can contact
• Lifeline: 0800 543 354 (available 24/7)
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• Youthline: 0800 376 633
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• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• Samaritans 0800 726 666
• If it is an emergency and you feel like you or someone else is at risk, call 111.
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