Douglas "Harry" Morton, 61, killed Gwendoline "Carol" French, 73, after offering to take her to Switzerland for the "Zurich option" of assisted suicide following her stroke.
Scot Mr Morton then plunged a kitchen knife into his heart and left a suicide note which read: "I have always believed we should decide the times of our departure from this planet."
The couple, who had been married 20 years, had enjoyed a globe-trotting lifestyle following their retirement.
But his wife's diminished ability to look after herself following a massive stroke in May last year triggered Mr Morton's obsession with suicide, Westminster Coroners' Court heard.
They were found dead at their home in Stormont Road, Battersea, southwest London, on November 20 last year.
Coroner Dr Fiona Wilcox said it was unlikely to have been a suicide pact and ruled Ms French was unlawfully killed by Mr Morton.
She said: "The court heard that Harry Morton and Carol French were a devoted couple. He met Carol when he was 21 and she was 34 and they were inseparable from that point.
"Every one of the many friends of Carol and Harry giving evidence today have commented on Carol's optimism, determination and commitment to improve and there has been no suggestion at all that she wished to end her own life."
She went on to say: "I am satisfied that there is no convincing evidence that Carol wished her life to be ended at this time."