David Edmonds, who has been a director of the company that controls the Olympic Park since 2009, offered his resignation to London mayor Sadiq Khan last night.

The announcement comes after the London mayor announced on Tuesday evening that he had ordered an investigation into the rising bill for converting the London Stadium.

When Balfour Beatty first secured its contract to convert the stadium it was expected to cost £190m. But after specification changes needed to strengthen the foundations and steelwork for the largest cantilevered roof in the world, the contractors were granted extra cash two years ago taking the cost to £273m.

The development and evolution of the retractable seating has also turned out to be more expensive than first expected.

Yesterday it was revealed that it the conversion costs have now jumped by another £51m to £323m. Together with the £430m original Olympic build, the stadium project has now cost over £750m.

Edmonds chaired the investment committee, and was the first chair of E20 LLP, the joint venture between LLDC and the London Borough of Newham, owners of the Olympic Stadium.

The LLDC confirmed the news in a statement today, but did not explicitly cite the new inquiry as Edmonds’ reason for stepping down.

“David has made an enormous contribution to the legacy of the London 2012 Games and he has helped to steer the organisation through some extremely challenging issues,” said David Goldstone, chief executive of the LLDC.