Simon Kirby will leave by the end of the year as project comes under fresh scrutiny from May’s new government

HS2 boss Simon Kirby is quitting the £56bn high-speed rail project before construction even begins, in order to join engineering giant Rolls-Royce.

Kirby (pictured) - chief executive of HS2 Ltd and the country’s highest-paid civil servant on a pay package of £750,000 - will join the Derby-based engine maker as chief operating officer at Christmas. A search is underway for his successor at HS2.

Kirby’s departure after two-and-a-half years at HS2 comes at a critical time for the project, which is coming under fresh scrutiny from Theresa May’s new government.

The Sunday Times reported May could step in and alter the scheme, with the eastern spur of phase two from Birmingham to Leeds thought to be particularly vulnerable. One source told the paper: “The new government is understood to want a new direction”.

The paper’s report also claims Kirby is joining Rolls-Royce at the second time of asking, after he was approached at the beginning of the year by the company, but that this earlier approach was turned down.

HS2 denied Kirby’s departure was linked to problems with the project, while the Department for Transport said the government “is committed to HS2 and has no plans to change the project”.

Parliament is set to vote on plans for the first phase from London to Birmingham by the end of this year, with building work due to start by the middle of next year.

Commenting on Kirby’s departure, HS2 chairman David Higgins said: “Simon has used his vast experience to recruit and shape a world class team which over the coming years and decades will turn HS2 into a reality that will be of lasting benefit to this country.”

Kirby said: “HS2 is not just a highly ambitious project, but also one which will leave a lasting legacy for Britain.”

Rolls-Royce chief executive Warren East said he was “delighted” Kirby had chosen to join the engineer, adding that his “exceptional track record in delivering complex major programmes” would boost the fast-expanding firm, which is significantly upping its aircraft engine and nuclear reactor production.

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