The 62-year-old surgeon told MPs: "What I found particularly disturbing was that a bomb would drop, maybe on a crowded, tented area and then the drones would come down."

His face shook with emotion as he paused for several seconds to compose himself.

He continued:"The drones would come down and pick off civilians - children.

"We [were] operating on children who would say: 'I was lying on the ground after a bomb had dropped and this quadcopter came down and hovered over me and shot me.'

"That's clearly a deliberate act and it was a persistent act - persistent targeting of civilians day after day."