The 85-year-old maestro had become virtually blind and had lost some of his hearing, while his 74-year-old wife had been suffering from cancer, according to a statement released by their son and daughter, Caractacus and Boudicca.
Rather than struggle on with their health problems, they decided to end their lives peacefully together last Friday, “under circumstances of their own choosing".
They follow more than 100 British people in making the journey to die in Switzerland, where assisted suicide is legal.
A Metropolitan Police spokesman said that detectives from Greenwich CID were investigating the circumstances of Sir Edward and Lady Joan's deaths.
A champion of English music and a devotee of Prokofiev but above all Verdi, Sir Edward was for many years associated with the Royal Opera House in Covent Garden, starting in 1952 as a lowly repetiteur. Music director Rafael Kubelik became his mentor and gave him his first breaks by allowing him to stand in at short notice when other conductors cancelled.
The second time this happened was a production of Verdi's Otello, with the leading exponent of the day Ramon Vinay playing the Moor. Sir Edward's success when he took over at a few hours notice started his lifelong love affair with Verdi's operas.
He left the Royal Opera House in 1970 to take up a post as music director to Australian Opera, conducting the first performance in the Sydney Opera House, but returned to London each year as a guest conductor.
He returned to Covent Garden full time as associate musical director in 1991, and over the years is reckoned to have conducted 950 performances of 49 different operas there.
He was also chief guest conductor, principal conductor and finally conductor emeritus of the BBC Philharmonic.
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