The London market hit 14-month highs in afternoon trading, as oil stocks rose driven by rising crude prices.
The FTSE 100 index edged 1.3 points higher to 6916, as Brent crude spot prices lifted 4.2% to just over $46 (£35.48, €41.24). Heavyweights such as Royal Dutch Shell rose 0.5p to 2005.5p.
However, in earlier trading top-flight shares hit 6,923.43 points, its highest level since June 2015. The FTSE 250 Index is up 130.2 points to 17937.7.
Trustnet Direct market analyst Tony Cross said: "Hopes over stabilising oil prices are playing a role here, news that unions have called off strike action in the North Sea is also helping sentiment here, too."
In the second tier, shares in the group that owns Garfunkel's and Frankie & Benny's jumped 15% after it ousted its boss after just two years in charge.
Restaurant Group said Danny Breithaupt will leave with immediate effect and will be replaced by Andy McCue, the former boss of bookmaker Paddy Power. The FTSE 250 group had posted a profits warning in April, but today shares rose 56p to 432.8p.
In afternoon trading the biggest risers on the FTSE 100 Index were Coca-Cola HBC (+48p to 1,729p), Marks & Spencer (+9.7p to 351.2p), easyJet (+27p to 1,086p), Whitbread (+98p to 4,048p) and Tesco (+3.2p to 159.7p).
The biggest fallers on the FTSE 100 Index were Rio Tinto (-74.5p to 2,414.5p), Antofagasta (-14p to 518p), Anglo American (-23.1p to 861.8p), Randgold Resources (-195p to 8,450p) and Fresnillo (-43p to 1,929p).
In afternoon trading the biggest risers on the FTSE 250 Index were Restaurant Group (+56p to 432.8p), Ibstock (+12.5p to 173p), Pagegroup (+21.8p to 370.9p), Polypipe Group (+16.2p to 282.5p) and Mitchells & Butlers (+12.1p to 261.1p).
The biggest fallers on the FTSE 250 Index were Genus (-194p to 1,744p), Hochschild Mining (-10.5p to 292.5p), AG Barr (-16p to 510.5p), Ocado Group (-7.2p to 294.5p) and Beazley (-8.7p to 395.5p).