By Preeti Upadhyaya, MarketWatch LONDON (MarketWatch) -- U.K. stocks traded lower Tuesday as the market awaited comments from Federal Reserve Chairman Ben Bernanke and as security firm G4S PLC got hit with a downgrade following its Olympics contract failure. The FTSE 100 fell 0.4% to 5,641.32. Bernanke's much-anticipated testimony in Washington is expected to color trading in Tuesday's markets, with investors keen to hear if he will make an announcement about a possible third round of quantitative easing by the U.S. central bank. London investors also digested data on U.K. consumer prices, which fell 0.4% to 2.4% in June from May. "U.K. inflation dropped sharply in June to its lowest since November 2009, further alleviating the squeeze on incomes and helping to revive consumer spending," said Chris Williamson, chief economist for Markit, in a note. "However, the same factors that helped push inflation down may soon reverse and drive inflation higher again in coming months," he added, citing prospects for rising food and oil prices. Among individual movers, shares of G4S extended losses from Monday, falling 3.9% as it was downgraded to neutral from buy by Bank of America Merrill Lynch. The U.K.-based firm recently announced it expected to lose up to $78 million on its Olympics contract after coming up short in terms of security staff. The London games begin July 27. Also lower, plumbing firm Wolseley PLC dropped 3.4% following an announcement that it will "explore strategic options" for its businesses in France amid difficult business conditions in Europe. Shares of Rio Tinto PLC (RIO) fell 2%. The mining giant reported strong second-quarter earnings, but Chief Executive Tom Albanese cited "global economic conditions and sentiment" as reasons for being cautious moving forward. Further weighing on the index, shares of Vodafone PLC (VOD) moved down 1%. Banking heavyweight HSBC PLC dropped 0.7% following allegations of money laundering. However, Barclays PLC picked up 1.6%, as investors shrugged off continued scrutiny of the bank's involvement in the Libor rate-rigging scandal. Energy firms also were on the rise as oil prices advanced, with heavyweight BP PLC (BP) up 0.3% and AMEC PLC gaining 1.3%.