One of Muammar Gaddafi's closest confidantes, who fled Libya after the revolution, has been sent back from Mauritania, where he sought refuge, to face charges which are likely to include civil rights abuse and mass murder.
As Libya's head of intelligence, Abdullah al-Senussi had been described as the man who knew the innermost secrets of the regime.
He has been linked to atrocities abroad and at home, including the Lockerbie bombing, the murder of British police constable Yvonne Fletcher, the blowing up of a French airliner and the slaughter of 1200 prisoners at the Abu Salim prison in Tripoli.
The delivery of Senussi by the Government of Mauritania, after months of negotiations, is a diplomatic victory for the new administration in Libya.
But it is another setback for the International Criminal Court, which had wanted to try him in The Hague for crimes against humanity.
The ICC has also failed in its attempts to get custody of Gaddafi's son, Saif al-Islam, who is likely to be tried in the Libyan town of Zintan, where he had been held since his capture last year.
Senussi had been held in Mauritania after arriving six months ago on a flight from Morocco disguised as a Tuareg tribesman. His extradition followed the visit this week of a delegation led by the Libyan Justice Minister.
Libyan television showed Senussi, heavily bearded and smiling nervously, emerging from a helicopter in Tripoli surrounded by soldiers. The chief spokesman for the prosecutor general's office in the capital, Taha Baira, said: "We received Senussi and he will undergo medical tests. Soon he will also undergo interrogation for the cases he has been charged with and for which he will face trial."
The Mauritanian Government, which had previously insisted it would first put the former spy chief on trial over his illegal entry before considering claims from other countries, said yesterday it had agreed to the handover after receiving guarantees from the Libyan government that the prisoner would not be mistreated.
The French Government has sentenced Senussi to life imprisonment after a case heard in absentia, involving the shooting down of a UTA airliner over Niger in 1989 in which 170 people were killed.
It has also been claimed that he was involved in the 1988 destruction of the Pan Am flight over Lockerbie. However, Libya became a staunch ally of the West against Islamists after the rapprochement with Gaddafi led by the US and Britain, and Senussi will have details of co-operation which could cause embarrassment on both sides of the Atlantic if aired publicly.
This year, US House Minority Leader Nancy Pelosi, who led a delegation to the region, said Washington had a "particular interest" in seeing Senussi arrested "because of his role with the Lockerbie bombing".
But a trial in Libya will focus on Senussi's part in crushing dissent and the role he played in the Abu Salim massacre when, according to some accounts, he ordered guards to open fire on detainees.