A mountain leader described how a killer polar bear knocked him to the floor and clawed his face minutes after killing a teenage boy.

Andrew Ruck, 27, from Brighton, told an inquest the bear charged into his group’s campsite during an adventure holiday to the remote Norwegian Svalbard Islands in August 2011 with the British Schools Exploring Society.

Horatio Chapple, 17, was sleeping in his tent when the bear stormed the site and mauled him to death.

Describing how he woke up and saw another group member firing a rifle at the bear, Mr Ruck said: “I woke up straight away and sat bolt upright, I then remember Spike [group leader Michael Reid] or I opening the tent to see the polar bear there. I do not think it had anyone or anything in its mouth at that stage.

“He [Reid] tried to fire the rifle four times, bullets emptied out. He shouted: 'It's not working' and then the bear came over to him and knocked him to the floor. After that I exited the tent through the other entrance. I just charged towards the bear, shouted and picked up rocks and threw them at its face.

“I remember the bear then attacked me and knocked me straight to the floor, its paws were on my shoulder, I remember seizing its face. It swiped my face with its claw and my head would have ended up in its mouth at some point.

“The bear left me for some reason but I had very few clear thoughts after that.”

At the inquest at Salisbury Coroner’s Court Mr Ruck said a decision had been made to use a tripwire system as an early bear-warning alert.

The system has been criticised at the inquest for having missing components and for working inconsistently. Four other group members were hurt before the bear was shot dead at the campsite, where the group, known as Chanzin Fire, had been staying.

The inquest of Eton pupil Horatio Chapple, from Sailsbury, Wiltshire, continues.