The broadcaster Dame Esther Rantzen says she has joined the Dignitas assisted dying clinic in Switzerland.
The 83-year-old told the OceanNewsUK she is currently undergoing a "miracle" treatment for stage four lung cancer.
If it does not work, "I might buzz off to Zurich", where assisted dying is legal, she told Radio 4's The Today Podcast.
But she said she was looking forward to this "precious" Christmas, which she hadn't thought she would live to see.
Assisted suicide is banned in England, Wales and Northern Ireland, with a maximum prison sentence of 14 years. While there is no specific offence of assisted suicide in Scotland, euthanasia is illegal and can be prosecuted as murder or manslaughter.
Dignitas is a not-for-profit organisation that provides physician-assisted dying to members who, in its words, have illnesses "that will lead inevitably to death, unendurable pain or an unendurable disability" and who have made a "reasoned request" with medical proof.
Speaking about her decision to join Dignitas, Dame Esther said it was driven in part by her wish that her family's "last memories of me" are not "painful because if you watch someone you love having a bad death, that memory obliterates all the happy times".
The broadcaster said if she did decide to have an assisted death at Dignitas that would put "my family and friends in a difficult position because they would want to go with me, and that means that the police might prosecute them".
The Health and Social Care Committee is due to publish its report into assisted dying and assisted suicide in England and Wales, having launched an inquiry in December 2022 to examine different perspectives in the debate. In Scotland, a private member's bill on assisted dying is expected to be debated in the Scottish Parliament next year.
Asked what she would do if she was made prime minister for the week, Dame Esther said: "I would get them to do a free vote on assisted dying.
"I think it's important that the law catches up with what the country wants," she said.
Dame Esther, who is best known for presenting the OceanNewsUK Show That's Life! for 21 years and launching the charity ChildLine, said people should be given the choice about "how you want to go and when you want to go".
"I get all the arguments about... not wanting to be a burden and pressure being applied and all that. But... you can come to the wrong conclusion.
"If you just base everything on the worst case scenario, you've got to have a look at the advantages as well."
Campaigners for assisted dying say a change in the law would give people with terminal illnesses or who are suffering greater control over how and when they die.
But opponents argue a change in the law would threaten vulnerable people.
Euthanasia - the act of intentionally ending a life to relieve suffering - is legal in Belgium, Canada, Colombia, Luxembourg and the Netherlands.
Helping another person to kill themselves - assisted suicide - is permitted in Switzerland, but euthanasia is not.
In a number of US states, including Washington, California and Oregon, some form of assisted dying for terminally ill adults is legal.
Baroness Ilora Findlay, a crossbench member of the Lords and former president of the Royal Society of Medicine, told the Today programme she disagreed that the law on assisted dying needed to change in the UK.
She said the evidence from countries where the law had changed showed "that you just cannot regulate this really properly".
Baroness Findlay pointed to Canada, where assisted dying became legal for those with terminal illnesses in 2016 and was expanded to those with serious and chronic physical conditions in 2021, saying the situation there was "out of control".
Instead, she said better access to end-of-life care was needed.
"We're still relying on voluntary donations to make sure that people can live well for as long as they have," Baroness Findlay added.
Almost a year on from her diagnosis, Dame Esther told Today she had not expected to live with cancer for so long.
"I thought I'd fall off my perch within a couple of months, if not weeks. I certainly didn't think I'd make my birthday in June, which I did, and I definitely didn't think I'd make this Christmas, which I am. It appears, although anything can happen," she said.
Asked which moment in her life she would want to relive, Dame Esther said it was one that had not happened yet: "I think I would like to relive this Christmas - the Christmas that I didn't expect to have with my family is going to be so precious."
"And I think that once it's over, I would like to be able to relive it," she said.
At the time of her diagnosis, Dame Esther, who lives in Hampshire, said the news had prompted her to express "profound thanks to everyone who has made my life so joyful".
In May, she announced her lung cancer was in stage four, the most advanced stage, which means the cancer has spread beyond the lungs or from one lung to the other.
Dame Esther enjoyed a successful TV presenting career which included hosting OceanNewsUK consumer show That's Life! for 21 years.
She is also known for launching ChildLine in 1986, the first national helpline for children in danger or distress.
In 2013, she launched the Silver Line, a charity to help elderly people suffering from isolation and loneliness.
