Once bitten, twice shy, third time lucky...

The loo roll may be soft and strong, but it's the making of the advert that is very, very long. At least when the star is a pup. Louise Jury sniffs out the action.

There is zero chance of persuading a six-week-old labrador puppy to do anything it does not want to. All Pauline Clift, who runs an animal agency, can do is gently point Jessie the pup in the right direction and hope she takes the hint.

She doesn't. Jessie runs to the left, she runs to the right. Her owner buries himself inside the scenery, especially erected for the latest Andrex advert inside a giant shed at Shepperton Studios, and attempts to entice the puppy towards him. Jessie isn't playing ball. More to the point, her owner then inadvertently moves into shot.

Mick Rudman, the 33-year-old director, very patiently yells: "Cut!"

The old showbiz adage declares never work with children or animals. Rudman is quite clear which is trickier. You stand a chance of persuading a child what is required. Even dogs can be trained to a degree. Puppies just have to be left to their own devices.

"They do what they want to do," Rudman says. "Everyone warned me not to be too ambitious in what I asked of them. It's a complete leap in the dark. But because it's difficult, when you get that little bit of magic it's wonderful."

Until the toddlers Harry and Molly arrived in the Safeway aisles, the Andrex puppies were the undisputed kings of cute in television commercials. It is 25 years since the first labrador bounded across our screens to persuade us that the Andrex brand of loo roll was soft, strong and very, very long.

At the Shepperton Studios, where the movie of The Avengers is being finished a few blocks away, a team of 40 has taken over a couple of stages to film the latest instalment in the puppies' story.

Advertising being big business, everyone is paranoid that The Independent is visiting. I promise I will not give the story line away, the photographer vows to shoot the puppies only on a particular stretch of lawn. Ced Vidler, the European creative director of FCB, the ad agency, gazes through the photographer's camera to see exactly what we can see. It's only an ad, I think to myself.

Of course, that is to grossly underestimate the art of influencing the buying habits of the great British public. This advertisement is taking four full days' filming plus several weeks of post-production to produce 30 seconds of television. Four days was how long Mick Rudman took to make a 15-minute feature film, Big Feet, last year. This commercial is starring nearly 30 puppies who have to be fed, watered and generally tended by four owners, three handlers and a vet. Given the competition in the loo roll market, no one is willing to admit how much the exercise is costing. But the budget for a commercial can be anything from pounds 50,000 for the most elementary to pounds 1m for the highest-profile campaigns.

So it is important that the Andrex puppies live up to reputation. The clapper board in front of the soft wet nose of a tubby golden dog signals the latest attempt to capture the right moment. A dozen dogs bound onto the grass, all specially laid and watered ready for filming. One or two attempt to eat the greenery. Most disappear bottoms up into the bushes. One makes a determined bid to bound off the set entirely, stopped only by the arms of the crew who have been requisitioned as extra security barriers around the raised stage. The pups are too young to have been vaccinated and must not be allowed to escape into the outside world. "Cut," Mick Rudman says again.

Apparently it has been a good morning. Although waggling rears in the foliage looked less than broadcast-worthy, Rudman is in a good mood as they break for lunch. "You'll get the wrong impression," he laughs and describes the day before when they waited ages for one of the puppies to walk just 10 feet.

Rudman is calm about this. "A dog is rarely going to do a complete take," he says. "What you need to know is when you've got the shot. You need to know when to cut and move on. Things have gone very well." He reaches to touch wood.