The London market struggled for direction in afternoon trading ahead of a widely anticipated speech by US Federal Reserve chair Janet Yellen. The FTSE 100 Index edged up 6.4 points to 6823.3, as traders waited for Yellen's speech at a high-powered financial conference at Jackson's Hole in the US where she is expected to hint at whether the central bank will raise interest rates before the end of the year. The FTSE 250 Index was up 27.8 points to 17910.6.
A rise in US rates from their ultra-low 0.25%-0.5% range would affect borrowing rates, contract prices and commodity prices all over the world.
Oanda senior market analyst Craig Erlam said: "The sounds coming from the Fed camp over the last couple of weeks appear to suggest that another rate hike is imminent and Yellen could use this event today to all but confirm this."
In the second tier, Frankie & Benny's owner the Restaurant Group said it will axe 33 sites and revamp its menus as the firm bids to turn itself around.
The FTSE 250 group, which owns over 500 UK outlets including Garfunkel's and Chiquito, ousted its chief executive earlier this month after poor sales.
The firm said operating profit fell 4.4% to £37.5m in the 27 weeks to 3 July, as the business "lost value-conscious customers".
However, shares lifted 16.6p to 424p, as investors were cheered by the firm's moves to change management, improve menus and cut underperforming stores.
In afternoon trading the biggest risers on the FTSE 100 Index were Glencore (+5.1p to 184.3p), Rio Tinto (+52p to 2441p), BAE Systems (+11p to 539.5p), Rolls-Royce (+10.5p to 784.5p) and Travis Perkins (+21p to 1703p).
The biggest fallers on the FTSE 100 Index were AstraZeneca (-60p to 4951p), Burberry (-14p to 1319p), Shire (-43p to 4859p), Unilever (-29p to 3530.5p) and Sainsbury (-1.9p to 240.5p).
In afternoon trading the biggest risers on the FTSE 250 Index were Amec Foster Wheeler (+41.5p to 578.5p), Restaurant Group (+21.7p to 429.1p), Shawbrook Group (+10.2p to 233.6p), SIG (+5p to 124p) and JRP Group (+3.7p to 103p).
The biggest fallers on the FTSE 250 Index were Worldwide Healthcare Trust (-78p to 2040p), Carillion (-8.3p to 273.4p), Pagegroup (-10.1p to 344.3p), Euromoney Institutional Investor (-29p to 1031p) and Ascential (-7.2p to 258.3p).