Britain's top share index steadied below a record high on Thursday as mining stocks rallied, though strength in the pound capped gains.

The blue chip FTSE 100 index was up 0.1 percent at 7,624.54 points by 0925 GMT, within a whisker of a record level reached in the previous session.

The UK's mining index traded at its highest level since mid-2014 as shares in Anglo American, Antofagasta, Glencore and BHP Billiton all rose between 0.8 percent to 1.1 percent, thanks to the underlying copper price hitting a fresh four-year high. Miners also dominated the action among British mid cap stocks, which were flat in percentage terms.

Shares in precious metals miner Hochschild gained 3.2 percent, while Kaz Minerals rose 1.4 percent.

"It's no real surprise to anyone that we're pushing all-time highs as we get deep into Brexit talks towards the end of the year," Henry Croft, research analyst at Accendo Markets, said. "But I think these latest highs have come predominantly thanks to gains for commodities, that on the back of U.S. dollar weakness."

Stocks trading ex-dividend weighed on the broader index, with shares in BT the biggest losers, down 2 percent, while Halma fell 0.6 percent. However, volumes were muted and individual price moves were limited with just two trading days remaining until the end of the year.

A rise in the pound weighed on big, international stocks such as British American Tobacco and Unilever, which declined 0.5 percent and 0.3 percent respectively. Looking back over the year, the FTSE's gains have been more muted in 2017, slightly underperforming the broader European STOXX 600 benchmark with a 6.7 percent gain. The STOXX 600 has risen 8 percent this year. Uncertainty surrounding Brexit talks continues to dampen sentiment around the region's equities, while a recovering pound has weighed on firms that source the bulk of their revenues overseas.

Sterling plunged in the immediate aftermath of last year's referendum on European Union membership, though the accounting-related boost helped UK blue chips seal 2016 with a gain of 14.4 percent.