A man has been arrested in connection with the murders of 21 people in the 1974 Birmingham pub bombings, West Midlands Police has said.
The 65-year-old was arrested in Belfast by counter-terror officers under the Terrorism Act.
His home is being searched and he will be interviewed under caution at a police station in Northern Ireland.
The Tavern in the Town pub was also targeted
In April 2019, an inquest jury found a botched IRA warning call led to the deaths of 21 people unlawfully killed in the atrocity on 21 November 1974.
Two bombs planted in the Mulberry Bush and Tavern in the Town pubs also injured up to 220 others.
Wednesday’s arrest comes just a month after home secretary Priti Patel said she would look into calls for a public inquiry into the bombings.
Ms Patel also wanted to visit Birmingham to meet campaigners, including Julie Hambleton, who is a member of Justice for the 21 and lost her 18-year-old sister Maxine in the pub bombings.
Responding to news of the arrest, Ms Hambleton called it “the most monumental event” in the criminal investigation into the bombings since the quashing of the convictions of the Birmingham Six in 1991.
When she was telephoned by a senior West Midlands Police officer with news of the arrest, she told of how she broke down in tears.
Priti Patel has said she would consider holding a public inquiry into the bombings
“I couldn’t speak, I was just inconsolable and was just looking at the picture of Maxine,” she said.
“It’s welcome news. It’s overwhelming news.
“It’s tangible progress,” she said, and “something we have been waiting a long time for”.
“Having this development – whatever happens – does not in any way lessen our desire for a full public inquiry to be held,” she said.
“There are wider issues which need to be examined, and so much that went wrong, like why six men were arrested for a crime they didn’t commit.”
She added: “How was it that for so long, after 21 people were blown up and more than 200 other innocent souls were injured, nobody was looking for the perpetrators?”
Nobody has ever successfully been brought to justice for the attack.