"Mubarak steps down" flashed up on their screens and traders called a halt to "pyramid selling", as the City's wags have named Egypt-inspired weakness.  The President's departure after 18 days of mass protest gave hope for greater stability in the region, saw the price of a barrel of oil fall 53 cents to $86.21 in New York trading and the FTSE 100 reverse a near-47-point decline to sign off the day back in the black and back above 6,000 points.  London's leading index rose 42.9 points to 6,062.9 as fund managers set aside fresh concerns for the sovereign debt of certain European countries and regained their appetite for risk.  Mining shares tracked metals prices higher, although the ceiling for both remained China, whose latest interest rate rise this week frayed nerves about demand for commodities.  Still, the platinum producer Lonmin added 67p to 18.45 and anglo american advanced 113p to ?34.21?. There was demand for power companies, too. Centrica continued to be chased higher on the familiar mix of fact and speculation. Credit Suisse lifted its target price on the owner of British Gas from 340p to 380p, while rumours persisted of a possible lucrative bid from either France's GDF Suez or, more likely, Gazprom, Russia's state-owned gas monopoly. Not new, but the shares ran 10?p higher to 344?p anyway.  BG was also lifted 51?p to ?15.24 by rekindled bid talk. BHP Billiton, the miner known as the "The Big aussie", up 41p at ?25.25, has been linked previously with the gas group.  SaBMiller, the owner of Peroni and Grolsch lager, rose 58?p to ?21.44 after a push from RBS, and Legal & General moved up 4p at 122?p after research from Nomura.  But it was a soggy end to the week for bank and shop shares. Banks, typically large holders of European government bonds, were marked lower generally after Portugal offered to buy back debt to try to soothe nerves about its ability to service it and Moody's Investors Service downgraded its debt ratings on half a dozen Irish lenders.  among those hit hardest was Barclays, 2?p lower at 311p before results on Tuesday. arturo De Frias Marques, Evolution Securities' banks analyst, urged clients to sell because, in his view, Barclays would struggle more than any other British lender to meet the new capital rules that he expects by the end of 2012. He told clients to switch from Barclays into Lloyds Banking Group, up 1p at 66?p. Losses were steep for retailers after the price of cotton ran past $190 a pound, a record, and another week of sales by the John Lewis Partnership, which includes Waitrose, proved something of a disappointment. In response, Next lost 63p to ?20, while Marks & Spencer fell 3?p to 368p. Kingfisher, Burberry and Supergroup were all lower, too.  Ocado, the grocery deliver company, tumbled 30p to 255p after the John Lewis pension fund sold