(BBC) William Barr was the US attorney general who announced the charges against Abu Agila Masud two years ago, on the 32nd anniversary of the Lockerbie bombing — the deadliest terror attack ever on UK soil.
He also announced the charges against Abdelbaset al-Megrahi and Al Amin Khalifa Fhimah in 1991 — the only people so far to have been prosecuted over it.
He spoke to BBC News as Mr Masud, who is accused of making the bomb which destroyed Pan Am flight 103, finally appeared in a US court on Monday.
Mr Barr told me the arrest sends an important message that no matter how much time has elapsed, anyone attacking the US will eventually be brought to justice.
