The last time Hiba Dabbas saw her brother Islam was in a dank room in the notorious Sednaya prison near Damascus on November 13, 2012. During the three-minute visit he begged her for more clothes and food, which she promised to bring with her next time.

But she would not see Islam again, or indeed learn anything of his fate until this month.

“After five years of silence we were told there might be news,” Ms Dabbas said. “We sent our cousin to check with the office of the local clerk, who looked up his name. And there it was, it just said “Dead’.

“We had expected this deep down, but somehow we still had hope he would walk out of there and complete his studies,” Ms Dabbas told The Telegraph from Egypt. “But all that time we were hoping, he was gone.”

The Syrian regime has quietly begun updating the records of some of the tens of thousands who disappeared inside its prison system. It is the first tacit admission that many of them died in government custody.