The FTSE advanced almost 1% in late afternoon trading as investors shrugged off concerns relating to Ireland's credit rating downgrade and disappointing US economic data.
Shortly after 3:30pm, London's leading index was up 0.89%, or 50 points, to 5,686.
Investors appeared unmoved after Fitch said Ireland would lose its AA- rating in favour of the lesser A+. It also said the unstable outlook meant it would be put on "negative watch".
British Airways, fresh from announcing a long-awaited joint venture with Iberia Airlaines and American Airlines, is up 5%.
Elsewhere, Anglo American and Kazakhmys were both up around 4% as metal prices strengthened on the back of a weaker dollar owing to speculation the Federal Reserve may implement a new round of quantitative easing.
Autonomy Corporation said it expects to show a year-on-year growth of profits equivalent to 35%, but investors were unimpressed. Shares in the software company slid 18% to £15.23.
Meanwhile, the Dow is flat at 10,950 in morning trade as investors mulled disappointing jobs data showing private sector employers cut 39,000 jobs in September. This was against a gain of 10,000 in August.
General Electric and Alcoa, both up over 1%, are among the day's early risers.
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