A woman who won a landmark case to travel abroad for an assisted suicide has died at a Swiss clinic, police say.
Mrs Z would have died through a self-administered lethal injection
The 66-year-old woman, known only as Mrs Z, had an incurable brain condition and died on Wednesday in Zurich.
Swiss police said her death was reported by Dignitas, a non-profit group which helps terminally ill people commit suicide legally.
Mrs Z won a High Court action on Tuesday allowing her husband to help her leave the country.
Family Division judge Mr Justice Hedley lifted a temporary injunction which had banned the trip, leaving it to the police to decide what action to take.
Mrs Z's husband could still face criminal proceedings on his return to the UK, as assisting a suicide is a criminal offence, punishable by a jail term of up to 14 years.
His late wife was diagnosed with the degenerative brain condition cerebellar ataxia in 1997 and had been cared for at her home by her local authority, which had gone to court to clarify its role.
Self-administered euthanasia is legal in Switzerland.
According to Dignitas, Mrs Z would have taken her own life by administering a lethal combination of drugs which sent her to sleep, followed quickly by death.
The clinic has helped more than 20 Britons take their own life since it was set up in 1998.
But the BBC's Imogen Foulkes, in Bern, said the Swiss authorities were becoming concerned by the flood of foreigners travelling there to die following widespread publicity about its euthanasia laws.
She said in 2000 only three foreigners came to Switzerland to commit suicide, compared to more than 90 in 2003.
Deborah Annetts, chief executive of the Voluntary Euthanasia Society, called for a change in UK law to allow people to take their own life without having to travel abroad, saying surveys showed 82% of the public supported it.
She said: "We wish to extend our heartfelt sympathies to Mr Z on his sad loss.
"The law has imposed this tragic journey upon him, as it has upon others, and it is to Britain's shame that more will follow.
"Mrs Z's dying wishes should have been able to be met within this country.
"The police and the CPS (Crown Prosecution Service) did not take any action to stop this, which shows that the Suicide Act is now unenforceable.
"We need a law that works and which is compassionate."
A private member's bill, submitted by crossbencher Lord Joffe, has been submitted to Parliament which would remedy this, she added.
The ProLife Alliance said it still opposed euthanasia but offered sympathy to Mrs Z's three children who, the High Court heard, supported her decision reluctantly.
Spokesman Patrick Leahy said: "They must be devastated.
"We look forward to the time when the UK offers palliative care to everyone to remove any desire for people to end their lives in this tragic way."
The widow of Merseyside pensioner Reg Crew - who flew to Dignitas's clinic in Switzerland in 2003 for an assisted suicide - said Mrs Z would have died in a good environment.
Win Crew, 72, was questioned by police on her return but no further action was taken.
She said: "They are wonderful people at the centre. They were very caring and very helpful and made Reg's end dignified.
"It would have been a good environment for her there and I know that was what she wanted."