The least popular varieties included Marks and Spencer's sparkling spring water, which was described as "metallic and bitter", and S.Pellegrino, one of the most expensive alternatives at £1.09 a litre.

On one of these wine-producing estates is the handsome granite and deep cherry-coloured Quinta de Vale Abraao, which forms the heart of the Aquapura Resort & Spa.Divided from the port centre of Peso de Regua by the river, the quinta was built in the 19th century.It is tucked down the end of a meandering, cobblestone driveway and is surrounded by vineyards and gardens.With arms around each other’s shoulders, they move imperceptibly forwards through the heaving swamp, at each step raising a knee above the surface.“The men say you are too tall and heavy,” calls out Maria Serpa Pimentel, the head winemaker and great-granddaughter of the vineyard’s founder.