A formal €7.2 billion ($8.58bn; £4.9bn) cash bid for Dutch media and research giant VNU could be made today (Friday) by a seven-strong group of private equity investment firms.

Prominent among the latter is 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.

Four other US firms - Blackstone Group, Carlyle Group, Hellman & Friedman and Thomas H Lee Partners - are participating in the bid, as are UK-based Permira Advisers and AlpInvest Partners of the Netherlands.

For well over a month the septet have conducted due diligence, reportedly with a fine toothcomb. Insiders say they are ready to bid up to €28.50 a share with a formal move tabled today. However, lips are zipped both in the consortium and VNU camps.

Sources close to VNU say that major shareholders will not be enthused by a bid at the level of €28.50. Investors have also expressed concern that the company is rushing into a deal to end a painful chapter in its history - last year's botched attempt to take over IMS Health.

Best known as the owner of the Nielsen Media Research television-ratings and ACNielsen market research businesses, VNU's assets also include a plethora of publishing properties including the Hollywood Reporter and Billboard magazine.

Data sourced from Wall Street Journal Online; additional content by WARC staff