Robert Tchenguiz is now believed to speak for a 27% stake in Mitchells & Butlers, the managed pub and casual dining group. Through his investment vehicle R20, the Iranian entrepreneur is thought to have acquired shares yesterday from Alliance Bernstein, the investment bank, raising his stake from 23%. Much of the position is held through derivatives – so-called contracts-for-difference (CFDs) – acquired by other banks. The development comes as it was reported that private equity firms who have been in talks with M&B about acquiring a stake move closer to a deal. Reports this morning suggest Bain, Permira and consortium of CVC and Blackstone have all been in discussions about acquiring a 29.9% share in the group. Some of the private equity firms, which have been carrying out due diligence on the business, are supposed to have submitted revised proposals to the board last week. But, it is still not clear how the buyout groups plan to structure such an unusual acquisition. And it has also been reported that rival pub group Greene King has had discussions with some of the private equity firms about purchasing a joint share of M&B.