Downes, long associated with the Royal Opera, was almost blind and losing his hearing. His 74-year-old wife Joan suffered from cancer.

The maestro joined the Royal Opera in 1952 where his first duty was as a prompter for Maria Callas. He rose quickly, debuting as a conductor the following year and eventually rising to associate music director. During his career with the Royal Opera he conducted 49 different operas in over 50 years.

During the 1970s he became the music director for the Australian Opera, and conducted the first performance at the Sydney Opera House in 1973. Downes also had a long relationship with the BBC Philharmonic Orchestra where he served as principal conductor and conductor emeritus.

“After 54 happy years together, they decided to end their own lives rather than continue to struggle with serious health problems,” said a statement from the couple’s son and daughter, Caractacus and Boudicca.

The couple died at an assisted-suicide clinic in Zurich operated by the Dignitas organization.

Although assisted-suicide is legal in Switzerland, it is against the law in Britain, and London’s Metropolitan Police is investigating the deaths.