The Alliance leader David Ford has been selected as Northern Ireland's new justice minister.
He is the first local politician to take responsibility for justice and policing in 38 years.
Mr Ford was confirmed in the post after securing cross-community backing from DUP and Sinn Fein assembly members.
He did not get the backing of the Ulster Unionists and the SDLP, who both put forward members from their own parties for the justice job.
The Ulster Unionists, who had voted against the devolution of justice powers, put forward deputy leader Danny Kennedy for the post.
The SDLP, who have consistently said the ministry should be theirs under the D'Hondt system, nominated the North Belfast MLA and barrister Alban Maginness.
Neither man obtained the necessary cross-community backing.
We have a duty to show we can provide partnership, leadership and delivery and ensure that all our people see the benefits of devolution
David Ford Justice minister
Before appointing a new minister, MLAs passed a vote to increase the number of devolved ministries at Stormont to include the new Department of Justice.
Mr Ford will be in charge of the department with more than 4,000 employees and a budget of nearly £1.5bn.
He is the first Northern Ireland Justice minister since Westminster took policing powers away from the old Stormont government in 1972.
Back then, the job was held by the Ulster Unionist MP, John Taylor, now Lord Kilclooney.
A Real IRA car bomb which exploded outside MI5's Northern Ireland headquarters early on Monday was timed to coincide with the transfer of the powers.
It happened at about 0020 BST outside Palace Barracks, in Holywood, County Down.
No warning was given and the bomb, which was in a hijacked taxi, went off as the surrounding area was being evacuated.
An elderly man was treated for minor injuries.
Speaking on the floor of the Assembly after his selection, Mr Ford pledged to work on behalf of all the people of Northern Ireland.
"I am fully conscious that I am not the unanimous choice of this assembly but I do say to every member of this house, that we have a duty together to provide leadership and if we didn't know that before, we sadly had a reminder of it at half past twelve this morning.
A bomb at Palace Barracks was timed to coincide with the transfer of powers
"We have a duty to show we can provide partnership, leadership and delivery and ensure that all our people see the benefits of devolution."
Mr Ford was elected leader of the Alliance Party in 2001 after Sean Neeson, who succeeded Lord Alderdice, resigned in the face of poor election results.
Last month he met the families of Bloody Sunday victims to apologise after he was criticised for calling the Saville Inquiry "pointless".
Mr Ford made the comment last November in a briefing note which was leaked to the BBC.
"It's clear in that e-mail I used a clumsy and inappropriate phrase which caused significant offence," he said.
"I have told the families that I regret I caused offence."
DUP MLA Lord Morrow has been appointed as chairman of the Stormont Justice Committee, which will scrutinise the work of Mr Ford's department.
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