Mr Crew's wife Win was with him when he died

Motor Neurone Disease sufferer Reginald Crew, 74, from Hunts Cross, Merseyside, killed himself with the help of the "assisted suicide group" Dignitas in Zurich.

Merseyside Police launched an investigation into his death, looking at whether his wife Win broke the law by helping him to travel to the clinic.

But they said on Wednesday that there was "insufficient evidence" and "no public interest" in pursuing prosecutions.

Chief Constable Norman Bettison thanked Mr Crew's family for their cooperation, adding: "I hope they may now find peace."

Mr Crew was thought to be one of the first UK citizens to take advantage of more relaxed laws on assisted suicide in Switzerland.

All of the subsequent investigations confirm that his decision was a rational one, taken by him alone Chief Constable Norman Bettison

Assisted suicide is illegal in the UK, despite a number of legal challenges.

Mr Crew, a former docker, had suffered from Motor Neurone Disease for four years.

He travelled to the clinic in January 2003 with Win and his daughter Jan, and died after taking a fatal dose of barbiturates prepared by a doctor.

Chief Constable Bettison said: "Following our initial investigation, I am satisfied that there is no evidence to warrant prosecution of any member of Reginald Crew's family, or any other person in connection with his death.

"It is clear that Reginald Crew, after a long and traumatic illness, decided to commit suicide.

"All of the subsequent investigations confirm that his decision was a rational one, taken by him alone and his death was not assisted in any substantial way by anyone under the rule of British law.

"Mrs Win Crew and her family have lived with Reginald Crew's declining health over recent years and have supported him throughout this difficult time.

"They have faced the distress of bereavement with dignity, courage and considerable care."