Mr Brooksbank is a brand ambassador for Casamigos tequila, a sponsor of last night's invitation-only Unicef Summer Gala, where tickets are priced from £8,000 to £25,000.
And ahead of the bash, he spent Friday afternoon aboard the classic 26ft 'gozzo' boat, exploring the caves and grottos dotted around Capri's coast.
Joining him were Rachel Zalis – a former editor of Glamour magazine who is now Casamigos's global director, and who soaked up the rays in a black bikini – and Maria Buccellati, a model turned fashion ambassador.
She wrapped her arm around him as they posed for an affectionate-looking Instagram snap to share with her 14,000 followers.
[...]
A source close to Jack told The Mail on Sunday that Eugenie hadn't joined him on the business trip to Capri because he was 'there to work at the ball'.
Sources say Jack's job was to keep an eye on the cocktail bar and schmooze with famous guests, who included singers Katy Perry and John Legend and supermodel Heidi Klum.