The jump, which marked the third consecutive quarter of recovery, was attributed mainly to higher output by business services, finance and construction.
GDP is now 1.6 percent higher than at the end of the second quarter of 2009, when the economy was still in recession, the statistics agency said.
The preliminary calculation of the growth rate was above the consensus forecast of 0.6 percent.
The preliminary figure is subject to revision as statisticians work through more data on the economy's performance. In the previous two quarters, the final figure was higher than the preliminary estimate.
Construction, which has been hit hard by a slump in Britain's housing market, increased by 6.6 percent, following two quarters of decline.
Business services and finance were up 1.3 percent, marking the third quarter of growth in that sector.
