Sheikh Yamani, the former head of Opec who terrorised the West with threats over oil supplies in the 1970s, returned to the fray yesterday when he warned that the price of crude could triple to $100 a barrel if there is a war against Iraq. His comments contributed to another torrid day on financial markets, where shares tumbled. The FTSE 100 index closed down 68.3 at 3,671.1, a level unseen since December 1995. In an interview in a German magazine DM Euro, Sheikh Yamani - who is now retired as Saudi oil minister but still close to the ruling family...