Mr Henderson was promoted from the role of operations director when the highly regarded Ralph Topping retired in 2014. Mr Topping had helped to make the company Britain’s largest listed bookmaker by adding online and international operations to its chain of high street betting shops.
The industry faces higher taxes and tighter regulation. A series of mergers among rivals has intensified the competition for William Hill as gambling companies increasingly market themselves to younger sports fans betting via mobile apps.
William Hill said that Mr Henderson had left with immediate effect, without giving any details.
Gareth Davis, chairman of William Hill, did not dispute that the CEO had been fired after more than 30 years with the company.
“There remain significant challenges and in the recent past online has not performed in line with our high expectations as a company at the forefront of the market,” he said.
Mr Henderson, who received £914,417 in salary and benefits in 2015, will be paid 12 month’s notice as per his contract but no bonus for 2016, the company said.
Shares in William Hill fell to a four-year low of 235.5p on June 24, the day after Britain voted to leave the European Union.
William Hill said its trading remained in line with the previous guidance, with an expectation to produce £260m-£280m of operating profit in 2016.
Gavin Kelleher, analyst at Goodbody Stockbrokers, said William Hill’s online performance had been very disappointing recently.
“In its European online business, amounts wagered have been declining on an underlying basis,” he said.
“Their competitor set have got an awful lot better in the last three years and have really raised their game, and William Hill has not been able to match them.”
Mr Davis said the strategy of diversifying the business by increasing the share of international and digital revenues remained valid, but Mr Henderson had failed in its execution.
“At a time of increasing consolidation and competition as well as regulatory impacts in our core market, it is key that the delivery of this strategy is accelerated and the board believe this is best led by a new CEO,” he said.
Philip Bowcock, chief financial officer, who joined in November, has been appointed interim chief executive while a replacement is sought, a process which Mr Davis said could take up to 12 months.
“Philip has a clear set of priorities for this transition period, principally the turnaround of the online business,” Mr Davis added.