Kohlberg Kravis Roberts, the US private equity group whose ravening takeover methods were immortalized in 1990 by the best-selling book Barbarians at the Gate: The Fall of RJR Nabisco, is among the potential predators circling Dutch media giant VNU, parent of ACNielsen.

Having overreached itself - and angered major shareholders - by an attempt to acquire IMS Health last July, VNU pulled the plug on the $7 billion (€5.76bn; £3.96bn) deal in November, thereby prompting the resignation of ceo Rob van den Bergh. The group also saw its share price plunge to a low that makes it vulnerable to takeover.

KKR in concert with other private equity firms Apax Partners, Blackstone, Carlyle Permira and Alpinvest are already running their collective slide-rules over VNU - although the consortium does not have full access to its target's accounts and is far from ready to mount a bid.

Also in lip-smacking mode is a consortium whose number includes Thomas H Lee Partners and Bain Capital.

On Friday VNU revealed it is ready to allow limited due diligence on condition the interested parties indicate by the end of January whether or not they are likely to bid.

But in a carefully stage-managed leak, a loquacious mole let it be known that the month-end deadline is not "etched in stone". Mewled the mole: "There is a lot of work to do", adding that that VNU's decision to open its books will "level the playing field" for the competing bidders.

Data sourced from Financial Times Online; additional content by WARC staff