Prem Watsa acquired 2.4 Million Marsh & McLennan Cos. shares worth $483 Million. It makes up 30.67% of their stock portfolio and is their biggest holding. Prem Watsa started to build up the position in Marsh & McLennan Cos. in Q2 2007. Since then they sold 853 Thousand shares. The stake costed the investor $75.5 Million, netting the investor a gain of 540% so far.