The trip leader of an expedition in which a Wiltshire teenager was mauled to death by a polar bear told the second day of an inquest how he wrestled with the predator as it attacked him after his rifle failed to fire.

Horatio Chapple, 16, was on an adventure holiday to the remote Svalbard islands in August 2011 with the British Schools Exploring Society (BSES) when he died.

The Eton pupil, from Salisbury, was sleeping in his tent when the bear went on the rampage, inflicting fatal injuries to his head and upper body.

Four others were hurt before the bear was shot dead at the camp site, where the group, known as Chanzin Fire, had been staying.

Also injured during the incident were Andrew Ruck, 27, from Brighton, 17-year-old Patrick Flinders, from Jersey, and 16-year-old Scott Bennell-Smith, from St Mellion in Cornwall.

Trip leader Michael Reid, 31, known as Spike, from Plymouth, told the Salisbury inquest that he was awoken by several people shouting "bear attack".

He then grabbed the group's rifle and left his tent.

Mr Reid said: "There were shouts of 'bear', or 'bear attack', male voices, from more than one person. Immediately I exited the tent through one of the doors with the rifle.

"The only priority was getting out as swiftly as possible and taking the rifle with me as this was a serious situation.

"The bear was close and it was on top of one of the YEs (young explorers) in their sleeping bags. I believe it was Scott Bennell-Smith.

"I was not focussing on other people other than the bear that was on top of person on the ground. I do not recall seeing Horatio.

"I cocked the rifle, took aim, aimed it carefully as I didn't want to shoot the YE, although it was close I didn't want to injure the YE or worse.

"So I took a carefully aimed shot at the bear in the chest area of the bear but the rifle didn't fire. I cocked the rifle again and took another attempt at an aimed shot at the bear.

"I do not know why this failure was happening and so I carried on this until the magazine was empty.

"The bear was very close so I was able to get a clear aim."

Describing how the bear then turned on him, Mr Reid said: "The bear then came and attacked me because the rifle was then on the ground beside me.

"I shouted 'Use your pen rounds' even though I hadn't briefed the others where they were stored overnight, and although they are not safe to use (in close quarters) they are better than this bear carrying on.

"I remember the bear biting my head and I thought the weakest part is the eyes so I tried to take out the eyes with my fingers, but was unsuccessful.

"Once it had moved off me I then recall asking 'Where is my rifle?' and someone said 'It's in your tent' and I found it there.

"With one of the rounds that was on the ground having been ejected, I cocked the rifle and fired the round at the bear as it was attacking someone else."

He said that this time the weapon worked and fired a shot at the bear.

The inquest has heard that the Mauser 98K rifle had a three-position safety catch mechanism which meant that rounds could be ejected if fired with the catch in the highest position.

Mr Reid said that he was unaware of this at the time and did not know which position the catch had been in at the time.

He said: "From the reports I have read, there's a chance that the safety catch had got up in that position."

Mr Reid said he had no recollection of seeing Horatio during the incident but went on to pay tribute to the youngster.

He said: "He was a member of our team, one of the best in our team if not the best in the whole expedition.

"He was a fine young gentleman with amazing potential, I enjoyed being on the expedition with him."

Mr Reid said a bear watch could have been held on the night of the attack but it would have left the team tired and left them vulnerable to cold-related illness during the coming day's planned long trek.

Mr Reid, who was seriously injured in the attack, added that although he believed the person he saw being attacked by the bear was Scott Bennell-Smith, from information he had since received this might be incorrect.

Mr Reid said the expedition had been supplied with an incomplete tripwire system, meaning they had to set it up in a triangle formation rather than the advised rectangular shape.

He explained that his group also had to improvise using a paper clip to modify the trigger system because the brass fittings were missing.

Mr Reid said: "The tripwire system in base camp worked inconsistently, the system that we tested at the ice-climbing camp on our first or second night out from the base camp operated 100 per cent when we tested it."

Any tripwire systems were not foolproof, he said, because the cartridge would not fire if the bear walked into the post, knocking it over, rather than the wire.

The inquest continues.