How the Belfast attack played into the hands of Britain's far right

Police and politicians in Northern Ireland are making repeated calls for calm after a man was viciously stabbed in the street. (Reuters: Isabel Infantes)

Young men in black hoodies and balaclavas throwing stones and firebombs and targeting cars and homes.

It's all so depressingly familiar, particularly in Belfast, where these scenes are playing out after disturbing footage emerged of a man, identified by police as a Sudanese asylum seeker, attacking another man with a kitchen knife in the north of the city.

The victim, Stephen Ogilvy, is reported to be in a serious condition with injuries to his eyes, face, neck and back.

He was saved by the intervention of bystanders, including a man wielding a stick used in the game of hurling.

A GoFundMe page set up for the "Knife Attack HERO" lauds him for his courage in stepping in "to defend his fellow Irish man".

Police have charged the 30-year-old alleged attacker, Hadi Alodid, with attempted murder.

Britain was a tinderbox even before this latest incident, with narratives about immigration, race and claims of a "two-tier" policing system dominating political debate in recent months.

While UK leaders have called for calm after the arrest, in many ways the Belfast attack has played into the hands of Britain's far right and its preferred talking points.

During the country's three decades of sectarian violence, The Troubles, the targets of the casual violence of the kind witnessed overnight in the Northern Irish capital could be the police, British soldiers, alleged informers, or people from the other side of the bitter Catholic-Protestant divide.

Protesters hold anti-immigration demonstrations in Northern Ireland and England after a Sudanese man is arrested over a "brutal" knife attack in Belfast.

Similar scenes erupted a year ago to the day in the little town of Ballymena after two Romanian teens allegedly sexually assaulted a local girl.

A year on, the writing was on the wall well ahead of the horrific act of violence in Kinnaird Street, North Belfast.

Anti-immigrant sentiment is surging in the UK, with Nigel Farage's Reform UK party achieving record successes last month in local elections.

Ogilvy's family on Wednesday, local time, released a statement condemning the riot that broke out the previous evening.

"We want to make it absolutely clear that overnight unrest is not welcome, and peaceful protest is the only way forward," their statement read.

"We have many migrants who make a deeply valuable contribution to our country, including in our healthcare system and hospitality sector and we depend