They have been the sages of the city, capable of solving the most intractable political problems and the selection difficulties of the England football manager in 20 minutes of conversation - all while negotiating rush-hour traffic on the Kings Road.

Now London’s famously talkative black cab drivers are offering more than simple solutions to the great questions of our time: they may also be trying to sell you something.

As companies scramble for new channels to communicate commercial messages, black cab drivers have been recruited to serve in the brave new world of word-of-mouth advertising.

Adrian Torlini, 41, from Aylesbury, Buckinghamshire, has been a cab driver for nine years, and feels able to talk about any subject. Lately, however, he has persistently informed his passengers of the delights of Bangkok.

“It’s not all ping-pong shows you know,” he says, as he manoeuvres up the Old Kent Road. “There’s the floating market, the tiger temple – the temples are out of this world. The food’s fantastic.”

This part of Mr Torlini’s repertoire has been paid for out of the marketing budget of the Tourism Authority of Thailand. He would quibble with the idea that his conversation has been bought for advertising. “It’s not like I’m paid anything for doing it,” he says. Instead he was flown out to Bangkok for five days, all expenses paid.

“I suppose that’s payment of a sort,” he says. “But I have never seen it as a job. They have just given me an experience. No one said I had to talk about it. They just know that if you send someone somewhere and they like it they are going to talk about it, and if they are a cab driver they are going to talk to lots of people about it.”

He is certain that he has helped many of his customers to see Thailand in a new light, just as he is sure that he has persuaded many passengers to visit Melbourne, where he and his wife took a ten-day “trip of a lifetime” courtesy of the city’s tourist board.

“Many people don’t have the first idea what it’s like,” he said. “But it’s got the Great Ocean Road, some beautiful parks, and it’s a very cosmopolitan city. The people are so friendly.”

Mr Torlini is an “ambassador driver” for Taxi Promotions UK. It is now launching a new service: Womad (Word of Mouth Advertising) Taxis, and Asher Moses, the managing director, believes that all kinds of products could eventually find a slot in the discourses of his drivers.

“Holidays is always going to be a favourite,” he said. “Now we are looking to spread to airlines too. Any kind of exhibition will work.” He admits that insurance and banking are harder sells, although products such as online poker are easy to sell as so many of his drivers are avid players.

Jim Stengel, who as global marketing officer for Proctor & Gamble controls the world’s largest marketing budget – $6.7 billion (£3.4 billion) - talks of a golden age of television marketing in the 1960s, when three 30-second television advertising spots were all that was needed to reach 80 per cent of any target market. Now, he says, it would require more than a hundred spots: there are more channels, many other forms of media, and viewers are more cynical.

Paul Marsden, of the marketing consultancy Brand Genetics, told The Times: “If Jim Stengel is saying this you know it’s serious. People are asking themselves, ‘How the hell do we reach people?’.”

Some firms have attempted stunts in supermarkets, cinemas and bars. CommentUK sends actors into supermarkets to buy vast quantities of a certain ice cream and hold loud discussions as to its merits. Another firm, Sneeze Marketing, which sends performers on to Tube trains, buses and street corners, describes the process as “penetrating consumers’ personal deflector shields”.

The next big thing in word-of-mouth advertising, however, is “buzz” marketing. Consumers fill out a questionnaire to prove themselves an influential “agent”, and receive free products that are not yet in the shops.

Much like Mr Torlini’s free holidays, it is thought that these free products have an inherent “talkability” – agents discuss them with friends and relatives and report back. Bzz Agents, a pioneer of this strategy, set up in Britain last year and has 100,000 agents.

The medium is the message

— Cadbury’s TV advert for Dairy Milk, featuring a gorilla playing In the Air Tonight, became a viral hit. It has been watched more than 1,750,000 times on YouTube and has been posted on Facebook and blogs

— Bebo recently began a video series, Kate Modern, which has product placement and branding messages in the scripts

— When Threshers discount vouchers were e-mailed to people all over Britain in late 2006, the off-licence chain said that a limited promotion had gone wrong. Some suspected a clever sales campaign

— The Blair Witch Project, Snakes on a Plane and the forthcoming Cloverfield films have benefited from viral marketing campaigns

— Burger King had a hit with its “advergame” Subservient Chicken, which was sent to inboxes in 2004

— In a campaign that made many husbands nervous, Renault sent e-mails with anonymous love letters and photos of a car to women. The company later apologised

Source: Times database