Advertising: Try to Top This One

King of Madison Avenue? No agency can hang on to that crown for long these days, thanks to an epic acquisition binge. Only two weeks ago, the merger of three large firms--BBDO International, Doyle Dane Bernbach Group and Needham Harper Worldwide--created the biggest agency in the world (estimated annual billings: $5 billion). But that superdeal appeared to have been surpassed last week when London's Saatchi & Saatchi agreed to buy Manhattan-based Ted Bates Worldwide for an estimated $350 million. Those two companies, which are expected to announce the deal early this week, will have billings of about $7.5 billion. Ted Bates, named for the late adman who started the company in 1940, has coined famous slogans for such clients as Prudential ("Get a piece of the rock") and Rolaids ("How do you spell relief?").