Julian Smith has been unceremoniously dumped as Secretary of State as part of Boris Johnson's Cabinet purge.
Mr Smith was appointed in July 2019. He spent just over 200 days in the job.
His departure comes just weeks after brokering the deal which restored the powersharing administration in Stormont.
He was thanked by historical abuse campaigners after helping to push through Parliament long-awaited legislation to provide compensation.
Mr Smith was called in to see the Prime Minister in his Commons office as the reshuffle began.
In another shock move, Sajid Javid quit as Chancellor after Number 10 ordered him to sack his team of aides, a source close to the former minister said.
Other senior ministers axed include Andrea Leadsom from her role as business secretary, Theresa Villiers from her post as environment secretary and Esther McVey, who attended Cabinet as housing minister.
The Prime Minister intends to "promote a generation of talent" in a reshuffle aimed at preparing the Tories for the future.
Spoke with @JulianSmithUK a short time ago to thank him for his help in getting devolution restored. We may not have always agreed (we did sometimes) but his dedication to the role was incredible. Best wishes to him and his family. Always welcome in Fermanagh. https://t.co/2hUzOWmRBS
— Arlene Foster (@DUPleader) February 13, 2020
Speculation about Mr Smith's position centred on the terms of the Stormont deal, amid Tory concerns it could pave the way for prosecutions of British soldiers.
But allies of the axed minister said it was "absolute crap" to suggest that Mr Johnson and Number 10 had not been kept informed of the process and details of the deal.
I’m not convinced he knew then what Stormont House - agreed by his government in 2014 - contained, he does now though and the sacking of @JulianSmithUK seems to be, among other things, an attempt to row back on the New Decade legacy commitments
— Allison Morris (@AllisonMorris1) February 13, 2020
Mr Smith tweeted that "serving the people of Northern Ireland has been the biggest privilege".
"Serving the people of Northern Ireland has been the biggest privilege," he said. "I am extremely grateful to Boris Johnson for giving me the chance to serve this amazing part of our country.
"The warmth & support from people across NI has been incredible. Thank you so much."
Other ministers thought to be vulnerable are prepared for a "brutal" process as Mr Johnson tries to boost the presence of female MPs in the ministerial ranks.
This is what Julian Smith did the night Stormont was restored - he hosted victims of historical abuse for a reception after helping them to get laws passed to provide long awaited compensation - he was the first SoS they said had listened to them properly https://t.co/FX8zPwadDD
— Jayne McCormack (@BBCJayneMcC) February 13, 2020
Campaign group Survivors and Victims of Institutional Abuse tweeted that Mr Smith was "a man of your word" who had "a kind caring heart for others less fortunate".
22 days ago. #Reshuffle https://t.co/GuNfWy58zH
— Darran Marshall (@DarranMarshall) February 13, 2020
We regret very much that Julian Smith is leaving the NI post. Of all recent Secretary of State’s he was the one who had the most positive and constructive engagement on legacy issues particularly the pension for the severely injured.
— WAVE Trauma Centre (@WAVETrauma) February 13, 2020
We wish him well. pic.twitter.com/y65ckvv5rW
Former Tory leadership contender Esther McVey, who attended Cabinet as housing minister, said she was "very sorry" to be sacked from her role.
"I'm very grateful to the Prime Minister for having given me the opportunity to serve in his government and he will continue to have my support from the back benches," she said.
Mrs Leadsom said it had been a "real privilege" to spend six years in Government, adding: "I will continue from the back benches to work to ensure everyone is treated with dignity and respect."
Ms Villiers said: "What the Prime Minister giveth, the Prime Minister taketh away: just over six months ago, I was delighted to be invited by the Prime Minister to return to government after three years on the backbenches.
"This morning he told me that I need to make way for someone new."
Geoffrey Cox lost his job as the senior law officer, saying: "I am now leaving the Government at the PM's request."
Universities minister Chris Skidmore also left the government, saying he would have "more time to spend" with his family.
He tweeted: "Got a promotion in the reshuffle to be a better Dad with more time to spend with this gorgeous little one.... Thanks everyone who I've had the chance to work with and the civil service teams that have supported me- you have all been amazing."
Got a promotion in the #reshuffle to be a better Dad with more time to spend with this gorgeous little one....
— Chris Skidmore (@CSkidmoreUK) February 13, 2020
Thanks everyone who I’ve had the chance to work with and the civil service teams that have supported me- you have all been amazing pic.twitter.com/RdvdMCEl1N
Female MPs in line for promotion during the reshuffle process include defence minister Anne-Marie Trevelyan, former Brexit minister Suella Braverman and Gillian Keegan.
Alok Sharma is expected to be promoted from his current Cabinet post at International Development, while Paymaster General Oliver Dowden - who attends Cabinet - is also in line for a bigger job.
A Number 10 source said: "The Prime Minister wants this reshuffle to set the foundations for government now and in the future.
"He wants to promote a generation of talent that will be promoted further in the coming years.
"He will reward those MPs who have worked hard to deliver on this Government's priorities to level up the whole country and deliver the change people voted for last year."
The most junior ministerial rank - parliamentary under-secretary of state level - is likely to have a 50-50 gender split after the reshuffle.
By the summer, Mr Johnson also aims to ensure that at least 60% of ministerial aides - the parliamentary private secretaries - will be women, up from 18% at present.
Other factors at play in this reshuffle include filling the vacant role in charge of the Cop26 UN climate summit following the sacking of Claire O'Neill and deciding whether Steve Barclay will return to Government after the Brexit department was scrapped following the January 31 departure from the European Union.
Senior ministers including Chancellor Sajid Javid, Home Secretary Priti Patel and Foreign Secretary Dominic Raab are expected to remain in place while Downing Street has confirmed that Grant Shapps will stay on as Transport Secretary.
Mr Johnson's senior aide Dominic Cummings had reportedly been seeking a wider cull of ministers and a shake-up of Whitehall departments but Number 10 insiders believe a more "conventional" reshuffle will be carried out by the Prime Minister.