Leading article: In the Gaddafi clan's end is Libya's new beginning

In one respect, the capture by pro-government forces of Saif al-Islam Gaddafi brings the victorious Libyan uprising to its appropriate conclusion. Until Saif was seized, it was just about possible for remnants of the old regime to hope that their defeat might prove temporary; now the revolution is complete.

The dead leader's favourite son and presumed heir was taken prisoner as he tried to flee to Niger, as other members of his family had successfully done before him. That he failed is the final proof that the Gaddafi clan's rule is over.

In almost every other respect, however, Saif Gaddafi's capture potentially causes as many problems as it solves. The first relates to his custody. Saif was taken prisoner in the south of the country and is reportedly being held by local militia forces in the northern town of Zintan. Whether the local militia will be prepared to surrender him to the interim government, and whether they try to exact a price in terms of senior posts or influence, will be a gauge of the real power of the Prime Minister, Abdurrahim al-Keib. Clashes between rival militias not far from Tripoli last week do not make this a superfluous question.

The second problem relates to his treatment. In capturing Saif alive, Libyan forces have done what they were not able to do with his father: popular rage could not be restrained when the injured Muammar Gaddafi was caught. But will it be possible for those baser instincts to be restrained for as long as Saif may be in custody? Ensuring that Saif Gaddafi is treated correctly, according to international requirements, will be a further test of the new rulers, both of their intentions and how far their authority actually reaches.

The third problem relates to the course of justice. The Prime Minister has pledged that Saif will receive a fair trial, and it is understandable that Libya's new rulers would want to have him tried under their jurisdiction. This could be cathartic for Libyans, while also validating the new government. Yet Saif is also wanted by the International Criminal Court, and there is an argument that the ICC and charges of war crimes should take precedence over any claims that Libya might have on the erstwhile favourite son.

There is an awkward conflict of interests here, and one that might equally have arisen with Saif's father, had he survived captivity. One suggestion is that a joint trial might be held in Libya, and that could provide a solution of a kind. But this is unlikely to be the first or last time that such a conflict might arise. It would be unfortunate if the first international exposure of Libya's new government were to be as one party to a bitter dispute about who should try Saif. This is not what the new Libya or its friends abroad need. The joint option should not be rejected out of hand.

Fourthly, and finally, there is the sensitive matter of Saif's international role as Gaddafi's chief envoy, and especially his interaction with the last British government. There is enough that remains murky in what has already emerged to suggest that there could be a great deal more to come out, and it is unlikely to be flattering to the British side. Saif's involvement with the London School of Economics has already cost that establishment its director, but the full extent and nature of the contacts that government, academia and business established with the Gaddafis, as the then Prime Minister, Tony Blair, set about his rapprochement with Libya is still largely a closed book.

There are probably many, in Britain and elsewhere, who might have hoped that Saif Gaddafi would meet a fate similar to his father's, and take his secrets to the grave. For both countries, however, it is far preferable that the full truth should be known, if only to reduce the risk of similar costly misjudgements in the future.