Greggs is set to report a bumper Christmas after launching its first festive advertising campaign, which starred superchef Nigella Lawson.

Analysts expect the bakery chain to be one of the big retail winners of the holiday period when it reports fourth-quarter results on Thursday.

These are set to show a rise in sales of six per cent on the previous year, excluding new shop openings, according to investment bank UBS.

'Domestic goddess' Lawson is famous for her cookbooks and TV shows with indulgent recipes. 

In the Greggs ad, she suggestively tucks into one of its festive bakes, hailing its 'succulent filling' and 'creamy sauce all wrapped up in the flakiest of flaky pastries'. 

She has huge influence with her tips. 

The phrase 'the Nigella effect' was coined in 2006 when sales of goose fat doubled at Waitrose and Tesco after she recommended using it for roasting potatoes.

Meanwhile, retail experts at Kantar expect supermarket sales to have topped a record £13 billion over the festive period. 

M&S, Tesco and Sainsbury's, which give trading updates this week, are all said to have had a strong Christmas.

Sales at Lidl rose above £1billion for the first time in the four weeks to Christmas Eve, a rise of seven per cent including new store openings.