When Luis Moreno Ocampo flew into Tripoli last month in what may prove to be the final flourish of his career as chief prosecutor at the International Criminal Court, he had the quieter figure of Fatou Bensouda backing him up. As usual, his mission got him headlines but not his man, Saif al-Islam.

Now, as the flamboyant Argentine's term at The Hague winds up, his Gambian deputy is set to take his place as the world's most prominent champion of international justice.

Her appointment, which will be confirmed at a meeting of the court's member states in New York this month, will be welcomed on her home continent which has grudgingly found itself to be the sole interest of Mr Ocampo. The 10 trials underway at The Hague involve the Central Africa Republic, the Democratic Republic of Congo, Kenya, Uganda and Sudan. Other investigations are looking at Ivory Coast and Libya.

The African Union (AU) has fulminated against what they claim is a prosecutor serving Western interests. The head of the AU, Jean Ping, was moved to observe: "We are not against the ICC. What we are against is Ocampo's justice, the justice of one man."

The consensus candidate, Ms Bensouda will be seen as a win for both sides in this tussle. She was the outgoing Argentine's preferred successor, and the AU was determined to see an African appointed. When Mr Ocampo steps down after eight years in mid-2012 his legacy will be hotly debated. The lawyer came to prominence representing the victims of a Nazi war criminal in an extradition hearing; and acting as assistant prosecutor in the landmark "junta trials" in his homeland.

He has carried his campaigning style over into the ICC, with an activist term as prosecutor during which notions of ultimate responsibility for crimes against humanity have been tested and most famously a sitting head of state – Sudan's Omar al-Bashir – has been indicted.

There is little in Ms Bensouda's CV to suggest she will be as noisy as her boss. She rose through the Gambian civil service without publicly clashing with the country's brutal and eccentric autocrat Yahya Jammeh, who just won an election not even the AU could endorse.

Her in-tray will be considerable. The ICC will have decided whether to proceed to trial against the suspected masterminds of Kenya's post-election violence. This week's high-profile extradition of Ivory Coast's former president Laurent Gbagbo will be waiting and with it the most persistent and damaging accusation made against the ICC, that of partiality, although her place at the helm will rob the ICC's lazier critics of their anti-Africa taunts.