Peter Kay gave Jonathan Ross the cake to mark Bonfire Night

Comedian Peter Kay, from Bolton, gave Mr Ross a parkin cake from Dutson's bakers, in Bury Road, to celebrate Bonfire Night.

Despite Jonathan Ross only eating a few mouthfuls, customers have been demanding the cake ever since.

Advertising experts have said the plug could be worth thousands to the shop.

Neil Dutson, who runs the bakery, said: "Peter came in and asked for a parkin loaf, and said 'the next time you see this it'll be on Jonathan Ross'.

Parkin cakes have sold out at the bakers

"We were sat there watching it and we couldn't believe it when he mentioned it.

"He carried on mentioning it two or three times."

The cake cost Mr Kay just 69p, but the profits for Dutson's could dwarf that.

Rob Brown, from advertising agency McCann Erickson, said: "It starts at tens of thousands a year to have someone endorse your product over a period of time.

"It can run into much more than that, hundreds of thousands or even millions.

"If you pay to endorse a product then you won't be allowed to publicise it on a programme like Jonathan Ross - the programme makers just won't allow it - so this kind of PR is priceless."