Blue chip shares hit a fresh mid-session record, as energy stocks were boosted by rising oil prices.
Brent crude futures lifted almost 1.5% to $52.3 a barrel, amid reports that Saudi Arabia and Russia have agreed to extend an agreement to cut output for a further nine months until March 2018.
The FTSE 100 Index lifted 12 points to 7447.4 in afternoon trading, easing back from a record 7,460.2 earlier in the session.
Heavyweight miners and oil majors dominated the top flight leaderboard, with BHP Billiton up 19p to 1183p, while BP was 7p higher at 467p.
IG market analyst Chris Beauchamp said: "A new record high for the FTSE 100 this morning was driven in no small part by oil firms, which have been boosted by further talk among oil ministers that more production cuts will be necessary."
The biggest afternoon risers in the FTSE 100 Index were Antofagasta (+14.5p to 788.5p), BHP Billiton (+19p to 1183p), Glencore (+4.3p to 289.3p), BP (+7p to 467p) and Anglo American (+13.5p to 1054.5p).
The biggest afternoon fallers in the FTSE 100 Index were TUI (-47p to 1143p), ITV (-4p to 188.3p), Next (-83p to 4262p), Shire (-70p to 4680.5p) and Johnson Matthey (-42p to 3088p).
The biggest afternoon risers in the FTSE 250 Index were Sophos Group (+25.4p to 366.6p), Dignity (+164p to 2694p), Hochschild Mining (+9p to 263.5p), Tullow Oil (+6.6p to 201.7p) and Kaz Minerals (+14p to 458.7p).
The biggest afternoon fallers in the FTSE 250 Index were Entertainment One (-6.7p to 230.2p), JRP Group (-3.4p to 128p), Allied Minds (-3.8p to 147.2p) and Thomas Cook (-2p to 94p) and Paysafe Group (-9.7p to 470.4p).