Fever tree Mediterranean tonic water, made with zesty lemon time from a small family farm in

province and essential oils from herbs that grow in the Mediterranean sunshine.

So if three quarters of your g and tea is a fever tree tonic,

maybe it's time to call it

a T and G.

Fever tree, mix with the best. Ooh that takes me straight to the med.

It's August 1941 in the glamorous Portuguese coastal resort of Estureal, about 15 miles from Lisbon. In the intimate lounge bar of the exclusive Hotel Palachio, two men sit in plush armchairs.

They are both smartly dressed, one in his 50s, the other in his 30s.

The younger man knocks back the last of his martini,

and the pair get to their feet.

They walk across the bar's distinctive checkerboard floor

and out into the warm evening.

A gentle breeze rustles through the trees as they pass the hotel's imposing white stone facade,

along the promenade and through the carefully manicured courtyard to the nearby casino.

When they arrive at its entrance, the younger man shakes a cigarette from a pack he's had specially made for him back in London.

He fits it to his long ebony cigarette holder and lights up.

A doorman steps aside and usher them into the casino. A jazz band is in full swing as patrons dine and dance. Gambling tables stretch in every direction.

But this is business as well as pleasure. The elder of the two, John Godfrey, is director of British Naval Intelligence, a man who trades in finding out the enemy's secrets while protecting those of his own country.

The younger man is his personal assistant, and it is his contacts who have persuaded him

that a night at the casino is worthwhile.

While the Second World War rages across Europe, Portugal has maintained its neutrality.

Lisbon and Esturel are luxurious havens for spies, places where they can carry out their business of espionage in comfort and relative safety, meeting informants and making exchanges. Godfrey's assistant. information The pair make their way to a backrat table and lay down some chips.

...