After succeeding his grandfather, he got into financial difficulties, as a penalised Catholic, and sold the family properties at West Grinstead and Harting, West Sussex.
He entered the household in Rome of the so-called "Young Pretender", the exiled Stuart claimant, recognised by Jacobites as "King Charles III".
Charles Edward Stuart appointed Caryll his Secretary of State and made him a Knight of the Thistle.
Caryll returned to France in 1777 and died at Dunkirk on 7 March 1788.
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