UK-based advertising giant WPP is to buy US rival Grey Global in a deal worth $1.31 billion .
New York based Grey Global is the world's seventh largest advertising company and has a number of blue-chip clients, including Procter & Gamble, 3M and Warner Bros.
WPP beat off competition from French rival Havas and a consortium of private equity groups to secure a winning place in the auction.
To avoid conflicts with existing WPP clients, particularly Unilever, Grey will be run as an independent unit within WPP.
The move is the latest in a string of deals by WPP, which last year acquired UK rival Cordiant Communications.
Last year Grey generated revenues of almost £800m and pre-tax profits of £41.1m.
