The Douro valley in northeastern Portugal is the home of Port.
The ancient Romans prized the juicy red wines from the steep banks of the Douro River, but centuries passed before the British transformed them into Port — what the book calls Britain's early version of central heating.
The famous Port firms were mostly begun by men with British names — Sandeman, Croft, Graham, Cockburn, Dow, Warre — and if Portugal is the mother of Port, Britain is certainly its father.
By the seventeenth century wine was regularly being fortified with grape spirits simply to keep it stable on the voyage to England, at first only about 3 percent.
Then the remarkable 1820 vintage produced wine that was naturally rich, ripe and sweet, and sales soared; the next year shippers added more brandy and added it sooner, arresting fermentation earlier to leave more sweetness.
Over many decades the quantity of spirits was incrementally increased, producing a wine that is both sweet and substantially fortified.
The name Port derives from the city of Oporto, a major port on the Atlantic at the mouth of the Douro — the golden river — and Portugal's second city; historically, barrels were floated down from the inland vineyards of the Upper Douro to Oporto in narrow, shallow-bottomed boats called barcos rabelos.
Touriga nacional, probably native to the Dão, is the leading powerhouse grape in many Port blends and is also used in the dry wines of the Douro, bringing richness, depth, a commanding tannic structure, deep colour and fine aromas.
