The $4.5bn move by Michael Bloomberg's eponymous information and technology company to reacquire Merrill Lynch's 20 per cent stake will not only consolidate his control, but also end one of its most enduring relationships.

Merrill was the first customer when Mr Bloomberg, a former Salomon Brothers executive, founded Innovative Market Systems in 1982. The company, later renamed Bloomberg, specialised in real-time securities data.