A man was arrested in Northern Ireland in connection with the murders of 21 people in the 1974 Birmingham pub bombings.
Counter-terrorism officers arrested the 65-year-old man at his home in Belfast on Wednesday afternoon.
The bombings took place in the crowded Mulberry Bush pub and The Tavern in Birmingham on November 21, 1974. Although the Irish Republican Army (IRA) was believed to have planted the explosives, it never claimed responsibility.
It was the deadliest attack on the British mainland in 30 years of Northern Irish violence.
A police statement said: "The man was arrested under the Terrorism Act and a search of his home is being carried out.
"He will be interviewed under caution at a police station in Northern Ireland."
The bombings, in which more than 180 people were injured, caused the biggest loss of life on the British mainland during the 30 years of conflict between mostly Roman Catholic nationalists, who favoured Northern Ireland’s unification with the Republic of Ireland, and Protestants wanting to stay in the UK.
The violence, known as The Troubles, in which about 3,600 people died, was largely brought to an end with the 1998 Good Friday agreement.
In one of Britain’s most notorious miscarriages of justice, six Irish men were later wrongly convicted of the bombings and spent 16 years in jail until they were exonerated and released in 1991.
One of those wrongly jailed said the police had advance knowledge about the attack but allowed it to happen.
However, an inquest last year concluded the bombs were planted by members of the Provisional IRA, and that a warning they gave was inadequate. It also concluded there was no failing by the police.
