The new leader of the British Labour Party has more in common with Sinn Féin than he does with Labour here.
Sinn Féin president Gerry Adams was among the first to congratulate Jeremy Corbyn on his election as the new leader of Labour in Britain.
Louth TD Mr Adams has been close to Mr Corbyn for many years and tweeted his "warmest congratulations", calling him a "good friend of Ireland".
"I have known Jeremy for many years," said Mr Adams
"He is a good friend of Ireland and of the Irish peace process. I wish him well in his new and challenging role as leader of the British Labour Party."
Mr Corbyn was once a member of the left-wing Troops Out movement.
He was also a regular visitor to the North during the Troubles and attended marches commemorating Bloody Sunday.
Mr Corbyn has always supported the ideal of a united Ireland and has been close to the Sinn Féin leadership for decades.
He was criticised by both Conservatives and his Labour colleagues when he invited Gerry Adams to the House of Commons in 1984.
Three years later, he observed a minute's silence after the SAS killed eight IRA members and a civilian during a Provo attack on a police base in Loughgall, Co Armagh.