A polar bear ripped open the tent of Wiltshire teenager Horatio Chapple and dragged him out causing "mortal wounds" to his head, according to an independent report into the tragic death during an Arctic adventure holiday.

High Court judge Sir David Steel describes the incident during his report commissioned by the British Schools Exploring Society (BSES) into the death in Svalbard, Norway, saying that all involved - including 17-year-old Horatio - had displayed great courage.

The publication of the report was delayed until today to coincide with the resumption of the inquest in Salisbury into Horatio's death.

In his conclusion, Sir David states that the expedition group, known as the Chanzin Fire, had followed the advice of the Norwegian authorities to use a trip-wire system to alert them to the presence of any polar bears.

But he said that this was inadequate as the warning would be too late and also the equipment used was defective. Sir David also said that rifle training needed to be over-hauled for any future expeditions.

Sir David said the attack, which "lasted no more than a few minutes" took place at about 7.30am on August 5, 2011, while the group was still asleep.

He describes how the bear had approached through the north-western side of the trip-wire system but none of the warning mines had exploded.

In the report in which the names of the people have been redacted and replaced with coded letters, Sir David says: "The bear appears to have initially made its way to the tent containing E7, E3 and Horatio.

"It would appear likely that the bear must have ripped open the tent on Horatio's side. It then dragged Horatio out causing serious, indeed probably mortal wounds to his head.

"The screaming and shouts of 'bear' woke the rest of the camp. E4 opened his tent. He could see that the remains of the tent had collapsed on E3 and E7.

"L2 emerged from the Leaders' tent at about the same time though not yet armed with a rifle. Horatio appeared to try and sit up or even attempt to stand whereupon the bear reared up and slammed into him. He fell to the ground. He was not seen to move again.

"In the meantime L2 had got hold of the rifle. He operated the bolt to seek to load and cock the rifle but it failed to fire. He operated the bolt on three or four more occasions without causing the rifle to fire. On each occasion a bullet was ejected on to the ground leaving the rifle empty.

"The bear then turned on L2 and mauled him about the head. L2 dropped the gun. L1 had previously emerged from the rear of the leaders' tent.

"With L2 disabled he was unable to pick up the gun as the bear was over it. In any event he realised that, having seen the attempts to shoot the bear fail, he needed the spare bullets but was not immediately conscious of where they were and shouted for help in finding them."

Sir David said that E4 then encouraged the other group members to stay calm before going to the leaders' tent where LI was unsuccessfully trying to load a pen flare.

He continued: "L1 then picked up a stone and threw it at the bear which duly got the bear off L2 but onto himself. He in turn was mauled badly. Thereafter L1 started to make his way over towards Horatio in case there was anything he could do for him."

E4 then retrieved the rifle from the leaders' tent and began searching for spare bullets as its magazine was empty.

Sir David said: "L2 was too badly injured to speak. Whenever he or L1 moved, the bear came back to them having from time to time been back to the prone body of Horatio.

"Having failed to find any bullets E4 came back out of the tent and found himself then chased by the bear. The bear thereafter went to E3's tent and attacked E7. E3 decided to make a break from his tent and in turn found himself attacked by the bear."

Sir David described how other members of the camp had managed to escape to about 20 metres from the scene.

He continued: "L2 now managed to find one of the bullets that had been ejected, went back into the front of the tent to retrieve the rifle, loaded the rifle and, as the bear came back close to him, shot it dead."

Sir David said the group then rallied and started to tend to the injured and calls were made for help from the local emergency services, although problems were experienced with the communications equipment, and the rescue team arrived by helicopter in a "remarkable 35 minutes".

Sir David said that a post-mortem examinatio of Horatio concluded that his death was caused by "extensive soft tissue and bone injuries to the face and neck including destruction of the right facial artery".

He went on to praise the group members for their bravery.

He said: "All members including not least Horatio demonstrated great courage in the face of the attack which started while the camp was asleep.

"Likewise considerable presence of mind was shown by the uninjured members of the party in the aftermath of the attack in tending to the wounded and calling for help."