California is one of ten US states where assisted dying is lawful and in some respects it’s a model for how the practice might work in Britain.

Introduced in 2016, it’s available to those who are terminally ill and are expected to die within six months. Patients must self administer the lethal medication - the same as what’s proposed in England and Wales.

BBC Medical editor Fergus Walsh travels to San Diego to meet 80 year old Wayne who’s planning to end his life. He’s terminally ill with heart failure and in excruciating pain from a severely damaged spine.

“I just don't see any merit to dying slow and painfully and hooked up with intubation and feeding tubes. I want none of it,” he said.

The programme hears from doctors and patients on both sides of the argument. Opponents warn assisted dying is putting the vulnerable at risk such as people with disabilities or mental illness.

Michelle Carter is 72 and has advanced cancer. She believes people should have a choice but has completely ruled out having an assisted death

“Suicide dying is not for me..I choose palliative care. I have God and I have good medicine,” she said.

There are important differences between the law in California and what is proposed here. Patients can get access to lethal medication in 48 hours in California. If assisted dying is legalised in England and Wales, it will take about a month for terminally ill patients to be approved.

Across California, around 1 in every 300 deaths is now medically aided.

But in Canada assisted dying accounts for around 1 in 20 deaths - that’s 15 times the rate in California - and one of the highest in the world.

The law was introduced in 2016 - the same as California - and is open to those with an incurable medical condition which causes intolerable suffering. Initially it was just for the terminally ill, but that requirement has been dropped.

In Canada, nearly all medically assisted deaths are carried out by doctors who inject the lethal dose. Fergus meets one doctor who has helped hundreds of people to die. She says she sees it as a “ sacred duty.”

But another tells him that Canada has “fallen off a cliff” when it comes to assisted dying and that it is being used as an alternative to social or medical support.

Finally Fergus returns to California to witness Wayne end his life surrounded by his wife and children.

“I’m all in. I’ve never had any question about it,” Wayne tells him

Reporter: Fergus Walsh Producers: Paul Grant and Camilla Horrox Technical Producer: David Crackles Production Management Assistant: Katie Morrison Editor: Clare Fordham