Keir Starmer was celebrating a significant victory in his bid to remake his party after Labour's ruling body backed his candidate to become its new General Secretary.
David Evans was selected by the party's National Executive Committee to become the party's newest campaign chief.
Mr Starmer's success in appointing Mr Evans represents a significant win in reforming the party, as the finely balanced politics of the NEC does not guarantee him a majority.
The NEC is made up of politicians, elected Labour members and crucially representatives from unions affiliated to Labour.
Left-wing members of the NEC and some unions had expressed scepticism of Mr Evans before Tuesday's meeting.
Six candidates were shortlisted for the key post, with Mr Evan's beating out Mr Corbyn's former policy chief Andrew Fisher to secure the top job.
Mr Evans was regarded as the frontrunner in the contest, with his backers including Morgan McSweeney, Mr Starmer's chief of staff.
A former Labour official, he worked as an Assistant General Secretary between 1999 and 2001 and is seen as having played a key role in Labour's landslide victory in the 2001 election.
But this success under Tony Blair, and links to Labour's moderate wing were seen by many as a hindrance on Mr Evan's CV.
Mr Starmer said: “I want to congratulate David on his appointment as General Secretary. He brings a wealth of experience to this crucial role and a clear understanding of the scale of the task ahead of us.
“I look forward to working with David to build a team that can help us restore trust with the British people and build a team that can win the next election.”
Labour's General Secretary leads the party's professional staff in running the party machine across the country - with their top job being getting the party in fighting shape for elections.
Mr Evans said: “It is an honour and a privilege to be appointed General Secretary of the Labour Party.
“We face a defining period in the history of our great party, with a global pandemic, an imminent recession and a mountain to climb to win the next election.
"Through the strength of our movement, I know we can rise to this challenge.
“I look forward to working with our party, trade unions and members to build a team that can win us the next general election and give us the opportunity to once again serve the British people in government.”
Mr Evans faces an inbox overflowing with difficult issues.
Not only must he rebuild the party after it shattering defeat in December's general election, but he will also be responsible for responding to the findings of an inquiry by the equalities watchdog into Labour's handling of anti-Semitism cases within the party.
The Equalities and Human Rights Commission's report is due in the coming months.
Another inquiry, set up by Mr Starmer, is looking into the leak of a report, written by allies of Jeremy Corbyn, which alleged that staff inside Labour purposefully mishandled complaints of anti-Semitism to discredit the former Labour leader.
That report, and its leak, are part of a fierce and ongoing civil war inside the party between the party's left and right.
An NEC source told the Mirror: "Keir urged NEC members to vote for David Evans. If Evans now takes us back to the toxic culture in HQ, purges of left-wing members and stitch ups of parliamentary selections exposed in the leaked report, his appointment will be the worst mistake of Keir's leadership.
"Keir and Angela both stood on election platforms promising to unite the party. Members won't forgive them if they allow a hard-right General Secretary to wage factional warfare against the left. They are responsible for making sure Evans fulfils their election promise to bring our party together, not tear it apart."
