LONDON, Oct 9 (Reuters) - Britain's economy probably grew at its fastest pace in over two years during the third quarter of 2012, but it is likely to slow sharply in future, the country's leading macroeconomic think tank said on Tuesday.
British gross domestic product rose 0.8 percent in the three months through September, up from 0.1 percent growth in the three months through August, the National Institute of Economic and Social Research (NIESR) estimated.
This is a stronger growth rate than the average 0.6 percent expected by economists in a Reuters poll , although the economy is still likely to shrink overall in 2012 due to a sharp contraction in the first half of the year.
Moreover, NIESR said the strong third-quarter rate of growth would not last as it was due in part to ticket sales for the London Olympics and the reversal of negative effects in the previous quarter from an extra public holiday.
"Stripping out the effects of special events ... suggests underlying growth is closer to 0.2-0.3 percent per quarter," the think tank said.
NIESR says its monthly GDP estimates are usually within 0.1-0.2 percentage points of the first estimate of quarterly GDP from the Office for National Statistics. The ONS publishes its first estimate of Q3 GDP on Oct. 25.
(Reporting by David Milliken; Editing by Catherine Evans)
Keywords: BRITAIN ECONOMY/NIESR