The leading share index bounced back from 12-month lows on Tuesday to finish above the 5,000 threshold after a volatile trading session. The FTSE-100 index plunged beneath under the psychological barrier as nervous investors waited for news of fresh monetary measures from the US Federal Reserve. In early trade, the index was down by more than four percent before rallying to close the session up 1.89% at 5,164.92 points.\"At times of extreme tension, it\'s common to see such see-saw movements,\" Renaud Murail from Barclays Bourse in Paris said.Traders also reacted to weak British industrial output data and rioting in London, which some analysts are blaming on the coalition government\'s austerity drive. \"As if the issues of eurozone debt, the US deficit and downgrade and stalling growth were not enough to create a mountain of angst, pictures of London ablaze and Syria in virtual civil war reminds us how close we are to severe social disruption,\" said David Hufton, an analyst at brokers PVM Oil Associates.Lloyds Banking Group (LBG) remained the most traded blue chip with investors exchanging 281 million shares, closely followed by Royal Bank of Scotland which saw 276 million shares change hands..Chemical group Johnson Matthey finished top of the FTSE 100 leaderboard, up 8.21% -- or 137 pence -- to close at 1,806.It was closely followed by InterContinental Hotels Group, which ended the session up 8.20% -- or 79 pence -- to finish at 1,042 pence.The company -- which owns the InterContinental, Crowne Plaza and Holiday Inn chains of hotels -- surprised investors by announcing that its net profits climbed 11% to $156 million (109 million euros) in the first six months of 2011 on sales growth in China and the United States.\"In the first half, we delivered a strong performance across each of our regions, driven both by increased occupancy from business and leisure travellers as well as progressive rate improvement,\" chief executive Richard Solomons said in a statement. Fresnillo was the biggest casualty with the silver producer down 7.26% -- or 131 points -- at 1,673.Royal Bank of Scotland was also under pressure as the beleaguered banking group saw its share price slump 7.26% -- or 1.05 pence -- to end the session at 26.21. On the currency markets, sterling fell back against both the dollar and the euro. At 1614 GMT, the pound was trading at $1.6196 and 1.1372 euros, compared to $1.6355 and 1.1514 euros at the same time on Monday.