Drinking Casamigos tequila with Princess Eugenie's husband Jack Brooksbank

As well as being Princess Eugenie’s husband, Jack Brooksbank is European Commercial Manager for Casamigos, a tequila created by George Clooney, Rande Gerber and Mike Meldman in 2013 initially for their personal pleasure.

Brooksbank invites me to sip the smooth spirit at Mayfair’s Isabel, named after the formidable grandma of silver-haired society restaurateur, Juan Santa Cruz, who resembles Clooney.

‘Shake it like you mean it,’ says Brooksbank of the salt-free Margaritas on ice starring seven-month rested reposado. The result evokes seasoned spring water, with the vital spirit clearly surfacing the cocktail.

Brooksbank, former manager of dusk-to-dawn tapas and tequila hotspot Tonteria, recalls his journey to landing the ambassadorial role. ‘I conventionally applied, then there were endless Skype calls with the Malibu bosses,’ he says. Brooksbank’s little black book also helped. But despite the glamour of the Clooney backstory and Brooksbank’s regal ties, getting the spirit listed relies on frequently meeting barkeeps, ‘knowing their birthdays and their family’s birthdays’.

Aromatic, textured, even chic, an Old Fashioned made with añejo aged for 14 months in a bourbon barrel rather than bourbon is a Damascene sip. Given how good the liquid is, I am surprised by how humble the bottle is. ‘A take on the sample bottle,’ says Brooksbank. ‘Like one you’d find in a Western, Clooney says, where you slide it down the bar, pull the cork with your teeth and pour a shot.’

Casamigos added a mezcal recently, made by a fourth-generation producer in the world mezcal capital, Santiago Matatlán, Oaxaca. Brooksbank says he loves the ‘smoky banana’ flavour of the spirit, made from split agave patiently roasted in earthen pits amid volcanic rocks, then crushed by a horse-drawn tahona wheel. For a quenching pudding, I flood lemon sorbet with citrusy blanco. ‘And George served añejo over vanilla ice cream at his wedding,’ says Brooksbank. ‘A dulce de leche-like hit.’