In total, it is thought some 750 roles will eventually be shifted there from the capital – part of a wider plan to move 22,000 civil servant jobs away from London by 2030.
Speaking in a video to staff, Mr Sunak said he was “really excited”.
And for the Conservative leader of Darlington Borough Council the feeling was mutual.
“We’re on top of the world at the news,” Heather Scott told The Independent. “Absolutely delighted.
“This will bring a huge economic boost not only to Darlington but the wider Tees Valley. It is just what we needed after a really hard year.”
It is not clear exactly where the new campus will be but Ms Scott said the local authority had access to modern office space that could be converted or it was willing to help locate a suitable site for a purpose built complex.
“We will do whatever we can to move this forward,” she said. “And we will do it as quickly as we can.”
The market town – population 92,000 – beat off competition from Newcastle, Leeds and Bradford which had all lobbied for the campus.
Exactly why it was chosen has not yet been said but there is no doubt it would have been politically attractive to Mr Sunak.
The town elected its first Conservative MP for almost 20 years in the 2019 general election and is surrounded by similar red-turned-blue parliamentary constituencies. It sits at the heart of the Tees Valley, which has a directly elected Conservative mayor, Ben Houchen.
Crucially, perhaps, it is also right on the doorstep of Mr Sunak’s own seat of Richmond in North Yorkshire.
Either way, reacting to the news, Debbie Francis, a board representative with the Northern Powerhouse Partnership, said: “This is a vote of confidence in north.
“I hope moving parts of government to our great Northern towns and cities acts as an incentive for other organisations and businesses to follow suit.”