Australian scientist David Goodall has ended his life at a euthanasia clinic in Switzerland, asking in his final words: "Why is this taking so long?"

The 104-year old had to answer twice the four questions - what is your name, what is your date of birth, why have you come to the clinic and do you know what will happen when you press this button? - that are asked of anyone seeking to undergo voluntary euthanasia because, due to his arthritis, he was unable to press the button to release the deadly injection on his first attempt.

David Goodall, 104, in a room in Liestal near Basel, Switzerland, where he ended his life.

Euthanasia advocate Philip Nitschke, who revealed he acted as "music director" during the Professor Goodall's death in Switzerland, said the Australian's final words were said "flippantly" and impatiently as if to hurry death.

In a "final day press release" which included new photographs of Professor Goodall's final hours, the prominent euthanasia campaigner said he was "proud to have been appointed ‘music director'".