(Reuters) - London's blue-chip index was dragged lower on Thursday by steep falls in heavyweight bank Barclays and utility Centrica, while a rise in new coronavirus cases in China jolted broader risk sentiment.Centrica skidded 13% to a near three-month low after its 2019 profit slumped by more than a third, leading the FTSE 100 to shed 0.8% after two successive days of gains.Barclays was a major drag on the bourse as it slipped 3.2%. Britain's financial regulators were probing historical..