Sage Holdings, which is backed by the Riverside Company, spent £90m on M: and DF King & Co, a proxy solicitation firm.
DF King forms the larger part of the deal, but the actual value of M: is undisclosed.
'In one sense this gives us a war chest to make strategic acquisitions,' said M: co-founder Nick Miles. He was bullish about the agency's future and said the deal confirmed his and co-founder Hugh Morrison's commitment to the firm.
'We had one approach for M: the day before we started in 2002,' said Miles. 'But we waited until something of value came along. This provides our broad-based and solid business with investment for the future.'
Miles said some of the funds would invest in 'new and experienced talent' at the agency.
Last July, M: was hired by the British Venture Capital Association to manage coverage of The Walker Report into private equity (PRWeek, 13 July 2007).
Anthony Hilton, p11.