Martin Lipton

The poison pill. Lipton, a founding partner of the New York law firm Wachtell, Lipton, devised the shareholder rights plan in 1982, which lets a board flood the market with cheap shares if a bidder crosses a set threshold, making a hostile takeover ruinously expensive. Delaware courts upheld it in 1985, and it became the standard defence. Critics argue it entrenches boards against their own shareholders.