* Q3 operating profit undershoots by 20 mln stg
* Tough trading report mirrors other bookmakers
* Warm summer kept gamblers away from betting shops
LONDON, Oct 3 Third quarter operating profit from William Hill undershot forecasts by 20 million pounds ($32.5 million) after sports results went against the leading British bookmaker and business slowed in its betting shops.
William Hill, which has expanded rapidly online and overseas in recent years and joined Britain's FTSE 100 index of leading stocks in May, warned that it may not be able to recover the shortfall by the end of the year.
Shares in William Hill showed only a muted reaction, dipping 0.3 percent or 1.3p to 410p by 0715 GMT.
The tough trading had been expected after smaller rival Ladbrokes issued a profit warning last week, its performance further weakened by problems in its online operations.
A summer heatwave in July in Britain meant that fewer customers used the betting shops that still remain an important part of the business for both companies despite the growth of betting through online and mobile applications.
In common with other bookmakers, William Hill also said that sports results, particularly in soccer, had for once been running in favour of gamblers.
"Given trading in the quarter, operating profit was around 20 million pounds below our expectations for this period," William Hill Chief Executive Ralph Topping said in a statement setting out trading for the 13 weeks to the start of October.
"While the fundamental performance of the Group remains good and there is time for the Group's shortfall versus internal expectation to be recouped should results turn in our favour, there can be no certainty that we will make up this shortfall before the end of the year," he added.
Overall underlying group revenue increased 4 percent in the third quarter, but operating profit fell 31 percent, or by 24 million pounds.
Under Topping, William Hill has become the market leader in online gambling in Britain and expanded into markets such as Spain and Australia through acquisition.