Television cook Delia Smith's newest book is the fastest-selling hardback of the year, after selling over 200,000 copies in its first two weeks.

Publisher BBC Worldwide has now taken over a million orders for How To Cook: Book Two, which was published on 9 December.

It sold around 110,000 copies in its first week - compared with 68,000 for the debut of J K Rowling's most recent Harry Potter novel and 55,000 for Thomas Harris's Hannibal.

Sales monitoring organisation BookTrack now believes around a quarter of a million copies have been sold.

Managing director Richard Knight said: "It's the fastest seller of the year without a doubt. It's certainly the biggest seller for the three years we have been doing this and is probably the best ever.

"A week at Christmas is like a month at any part of the year for sales. Cookery books and annuals tend to be the big ones but even so 110,000 in a week is a lot."

Retailer W H Smith sold almost 10,000 copies on the book's first day alone - a record for a non-fiction publication at the chain.

Knight added: "Normally a hardback book which sold 10,000 copies a month would be right at the top of the best-seller lists, but to sell this many is a real feat. Delia is a real phenomenon.

"If we looked at a normal week's sales for a cookery book in, say, September, we might expect around 6-700 copies of an Ainsley Harriott."

Smith's commissioning editor at BBC Worldwide, Viv Bowler, said she was "delighted" with the sales - even though the BBC Two series of the same name does not start until next month.

Her first TV show was Family Fare in 1973, and her first TV cookery course followed in 1978.

Smith's BBC books have now sold more than 12 million copies - including more than a million for How To Cook: Book One.