HS2 Ltd boss Mark Thurston leaves his role on Friday amid speculation the high-speed rail project will be cut further.
The 56-year-old, whose pay package was worth £677,000 in the last financial year, announced his resignation in July.
There has been widespread speculation in recent days that Prime Minister Risi Sunak is preparing to either scrap or delay HS2’s Birmingham to Manchester leg after being warned the price tag for the whole project may have soared past £100 billion.
The first estimate in 2010 for the high-speed railway between London and the North was £30 billion.
Mr Thurston is HS2 Ltd’s longest serving chief executive, taking on the role six and a half years ago.
When he announced he was stepping down, he said someone else should take over as the project transitions from construction to a “defining period” involving the installation of railway systems, such as track and signalling equipment.
The process for recruiting Mr Thurston’s successor has started.
HS2 Ltd chairman Sir Jon Thompson will become executive chairman for an interim period until a new chief executive is in place.