The battle for Cadbury is likely to spark the first contested mega-bid fought out of London since Royal Bank of Scotland's ill-fated intervention in Barclays agreed takeover of Dutch bank ABN Amro two years ago.

That proved a disaster, but a takeover of Cadbury could make sense to several rival bidders.

Last year's $23 billion (£14 billion) takeover of chewing gum giant Wrigley byMars knocked Cadbury off the top slot in the world's confectionary market.

Mars would face competition problems if its tried to muscle in even as a friendly bidder for Cadbury.

Similarly, Nestlé could not buy Cadbury's chocolate business. However, analysts point out it could join forces with Hershey which would take that, allowing Nestlé to buy Cadbury's chewing gum arm.

Nestlé chief executive Paul Bulcke declined to comment specifically, but said: “We are always open for opportunities but we have no plans for any major acquisitions in 2009 and 2010.”

Other consumer groups like Unilever, Danone and Lindt saw their shares shoot up between 3% and 5%.