The fall of Bashar al-Assad's regime has not freed all of Syria's prisoners.

Al-Sina prison holds more than 5,000 detainees in the north-east of the country, which is under Kurdish control.

These prisoners – including some Britons - are suspected fighters and supporters of the so-called Islamic State group. Most are said to have been loyal to it until its last stand in 2019.

The BBC's senior international correspondent, Orla Guerin, was given rare access to visit the jail.