The men from National Security Bureau were careful to blindfold Hisham al-Omeisy before they began beating him with metal chains in the dungeon basement. 

Every few days they would drag him from his prison cell and hang by his handcuffed wrists from the ceiling, but they were always careful to make sure he could not see them. 

“I didn’t see the faces of the men who were torturing me but I recognised their voices. I will never forget their voices,” the Yemeni political activist told the Sunday Telegraph. 

Mr Omeisy spent months in the captivity of the Houthis, the Iranian-backed rebel group fighting a grinding three-year war of attrition against the Yemeni government and its Saudi allies.  

As…