A snapshot taste test of coffee from the big chains Pret, Costa, Starbucks, Caffe Nero and the cafes at Marks & Spencer, was carried out by consumer champion Which? who brought in Giles Hilton, a tea and coffee merchant with Whittard of Chelsea.

Pret’s Americano, priced at £1.70, was described by Hilton as being ‘thin, with charcoal smell’, and got a rating of three, however topping the chart was Caffe Nero with a rating of nine for its ‘good body and taste’ Americano, costing £2.05.

Pret's cappuccino, at £2.10, also failed the test, with a rating of four. Hilton told the Daily Mail newspaper: "This was served with too much milk, which was over-heated by the steamer - this makes the milk taste caramelized."

The test suggests that coffee lover get what they pay for. The most expensive of chains, Caffe Nero, topped both categories.

A spokesperson for Pret a Manger commented on the findings: "Pret appreciates all customer feedback. Our coffee is organic, Fairtrade and Rainforest Alliance and we take enormous trouble over our blending and our roasting. This is a single test and we are very sorry he didn't enjoy his cup."

Costa, Starbucks and cafes at Marks & Spencer were all reasonably rated for their coffee.