The 'Delia effect' is already working wonders for Waitrose's sales, with the retailer forced to bring in imported reinforcements to meet demand.

Waitrose used the start of the British rhubarb season to kick off its first TV commercial campaign featuring Delia Smith and Heston Blumenthal and claims it sold the equivalent of 14 weeks' worth of rhubarb last weekend as a result.

Sales of other lines promoted in the ads had also been "staggering", said a spokeswoman.

Smith appeared alongside Blumenthal in a three-minute commercial break during Coronation Street last Thursday, and extolled the virtues of British rhubarb as she demonstrated how to cook a rhubarb and ginger crème brûlée.

The television cook-in was supported by press ads urging shoppers to "pop down to your local Waitrose or go online and pick up Delia's recipe card. You'll find all the ingredients together in store and right now, British rhubarb is in season and at its very best."

But Waitrose had been forced to bring in Dutch and German rhubarb supplies as a result of the upsurge, as well as a delay in the British rhubarb crop, it claimed. "Some of the British outdoor crop has been slightly delayed due to the cold winter, and our British growers have even taken the step of wrapping rhubarb in fleeces," said the spokeswoman. "We have sourced all the British rhubarb we could physically get our hands on."

Other ingredients promoted by the duo also saw extraordinary upsurges in volume sales last weekend, the supermarket said.

Volume sales of Waitrose Chinese Stem Ginger in Syrup and Waitrose Organic Ginger Powder rose by 3,100% and 3,500% respectively, while Total Greek Yoghurt was up 1,800% and Waitrose Jersey Extra Thick Double Cream rose 1,000%.

Blumenthal's roast dish inspired purchases of Waitrose Essential British Pork Loin Roast joint to jump by 4,000% the same amount the retailers would normally sell in 33 weeks.

Other supermarkets have also benefited, with Sainsbury's reporting a 21% rise in rhubarb sales and a slight increase in ginger. Tesco said its rhubarb sales had doubled since the ads.

"We'd like to thank Waitrose for boosting our sales," said Tesco's rhubarb buyer David Croxson.

In 2008, Smith said she did not consider it appropriate for chefs to back one supermarket over another. The tables have turned.

The first delia/Heston commercial drove up sales of...
Rhubarb +2000%
Chinese stem ginger 3,100%
Pork loin roast joint 4,000%
Jersey extra thick double cream 1,000%