Sue Gray has told the Covid Inquiry she does not believe the collapse of power sharing in Northern Ireland hampered the devolved government's ability to respond to the pandemic.
Her witness statement to the inquiry acknowledged ministers were only "picking up the reins" following a three-year power vacuum in early 2020, as fears about the arrival of Covid-19 intensified.
But she argued that there would have been nothing ministers could have done beyond the steps that members of the Northern Ireland Civil Service had already taken.
Gray, who is now Labour Party leader Sir Keir Starmer's chief of staff, was on secondment to the NICS as permanent secretary of Northern Ireland's Department of Finance when the pandemic took hold. She returned to Whitehall to become second perm sec at the Cabinet Office in 2021.
In her Covid Inquiry witness statement, published on Friday, Gray argued the circumstances that unfolded in spring 2020 were so exceptional it was irrelevant that there had been no ministers in place since the beginning of 2017.
"It is the case that that ministers were picking up the reins of government just as the pandemic was taking hold," she wrote. "However, the pandemic was unprecedented and it is unlikely that ministers, had they been in office immediately before that time, would have taken additional steps beyond those the civil service had already put in place."
Gray's statement acknowledged that the collapse of power sharing in January 2017 meant NICS was "generally unable" to implement new policies in the absence of an executive and a Northern Ireland Assembly.
She said the situation meant "there was inevitably a tendency for government, in the form of NICS, to be reactive rather than proactive".
But Gray added: "I do not believe that the absence of a power-sharing NI government impacted the response to Covid-19."
Her 28-page statement went on to say: "I remain very proud of DoF colleagues who stepped up in an exceptional way to deliver a range of support in the most challenging of times."
Gray said she believes sufficient staff were made available in her department to operate C3 Contingency Programme structures when they were required in the pandemic.
However, she added: "My view that Northern Ireland was not behind other parts of the UK in terms of ability to respond to the pandemic relates only to C3 structures."
Gray gave evidence in person to the Covid Inquiry last week.
Her contribution, which lasted less than an hour, saw her explain fundamental differences between the leadership structures in the NICS and the UK government – as well as the devolved administrations in Scotland and Wales.
She told the inquiry it was her experience that government departments in Northern Ireland had a "more pronounced" problem with siloed working.
The inquiry continues.