Merrill Lynch is preparing to break cover with WPP, the world's largest advertising group, in a cash bid for Tempus which should top Havas Advertising of France's agreed £425m (€670m) bid.

Merrill has an established relationship with WPP, but deals have until now been confined to the US. The bank has had to share its US relationship with Goldman Sachs and occasionally Dresdner Kleinwort Wasserstein, where contact was first built with Wasserstein Perella in the US before the Dresdner Bank merger.