Hashem Abedi is expected in court after he was extradited to the UK to face allegations he was involved in the 2017 Manchester Arena bombing.
The 22-year-old, who was raised in the city, fled to Libya days before his brother Salman Abedi detonated his suicide vest as pop fans left an Ariana Grande concert, resulting in the deaths of 22 people, while hundreds were left injured.
Among his victims were eight-year-old Saffie Roussos, from Leyland, Georgina Callendar, 18, from Tartleton, mum-of-three Michelle Kiss from the Ribble Valley and Blackpool school receptionist Jane Tweddle.
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Inquests into the killings have been on hold while criminal proceedings against Hashem Abedi remained in limbo.
But his arrival at a London airport on Wednesday, flanked by British police following months of work to return him to England, raises the prospect of a development.
Police said the Crown Prosecution Service had authorised charging Hashem, the younger of the two Abedi brothers, with the murder of the 22 victims, attempted murder and conspiracy to cause an explosion likely to endanger life.
He remains in custody at a London police station and is expected to appear before Westminster Magistrates' Court on Thursday morning.
Prime Minister Theresa May, Home Secretary Sajid Javid and Security Minister Ben Wallace all welcomed the extradition.
Abedi's case is expected to be moved up to the crown court following his first appearance before magistrates.