The bodies of John Lawrenson, 80, and his wife Caroline, 70, were discovered by a neighbour who visited the property to feed their pets.
Mrs Lawrenson had recently been diagnosed with cancer with a “relatively short life expectancy”. Mr Lawrenson had left a note saying: “I cannot live without her.”
The devoted couple, who had been married for 47 years, were found lying peacefully in bed at their 18th-century home in Great Waldingfield, near Sudbury, Suffolk.
Police who searched the property found a carefully researched dossier on planned suicide, an inquest at Bury St Edmunds heard.
Coroner Peter Dean said the pair had taken overdoses of a drug purchased from a vet in Mexico.
He added: “Mr Lawrenson explained in a letter that he could not live without his wife and they had started to research planned suicide on the internet.
“It was a very well organised suicide. Both left notes and the handwriting was analysed to ensure it was their own.”
Mr Dean recorded a verdict that the couple took their own lives.
He added: “It is clear they both understood the consequences of their actions. Our thoughts are very much with their family and all those close to them in these very sad circumstances.”
The couple were well known in the village, having served on church committees. One resident said: “They seemed fascinated by and devoted to one another. They were very much part of village life and will be missed terribly.”
Mr Lawrenson was a former general manager at Reuters international news agency and also founded a publishing company. Mrs Lawrenson was a retired secretary. They leave two adult children.