The third of Sir John and Leonie Leslie's four sons, Seymour loved chinoiserie and the very latest inventions. The most social and romantic of the brothers, he suffered crippling tuberculosis as a child and spent his youth lying on his back. With nothing better to do, he became fluent in French, English and German literature.
As a joke he applied for a job at Queen Charlotte's Maternity Home demanding three times the salary and a huge office. The interview board was impressed and offered him the job. He turned out to be a brilliant appeal secretary, raising millions to build the then ultra modern hospital in Hammersmith, and invented the famous 'Queen Charlotte's Birthday Ball'. He married happily and was due to receive a knighthood for his hard work, but instead he was kicked out with a tiny pension from the new National Health Service. Undeterred, he returned to Dublin and replicated the work he had done for Queen Charlotte's Maternity Home for the Adelaide Hospital.
He retired to Castle Leslie Estate in 1962 converting the west wing into a separate residence and remained ever youthful in mind and spirit. 'Whenever Seymour Leslie walks into a room, there's an instant party'. He died aged 86, and requested to be buried under a weeping willow in Glaslough churchyard rather than in the damp family vault.