An aid worker who was with Alan Henning in Syria when he was captured, said the British taxi driver was "abandoned" by the Government who "sealed his fate" after agreeing to join US-led airstrikes against Islamic State militants in Iraq.
Majid Freeman, a Leicester aid worker, spoke of his devastation at the news that his friend had been brutally murdered by the IS terrorists, blaming the MPs who voted for military action.
The 26-year-old told the Leicester Mercury he felt "sickened" when he saw the video of his friend's death, just hours after attending a vigil in Leicester to call on the terrorists to release their hostages.
"Alan just wanted to help the orphans and people of Syria," Freeman said, adding that he "was a very courageous, selfless individual who always tried to help others."
“He went to Syria. He knew he could not help everybody but he still went to try to make a positive change."
But, responding to the new of Henning's execution, former head of the Army Lord Dannatt today said the deaths of hostages were sadly "part of the harsh price" to be paid in confronting the "abomination" of IS.
"Our Government is now standing up to its responsibilities and part of the harsh price, while this takes time, is that sadly if they have hostages in their hands, these atrocious things seem to be happening and seem to be going to continue to happen," he told BBC Radio 4's Today.
Renewing his call for the UK to extend military operations to Syria, he said: "Dealing with half a problem is not going to solve the problem," he said.
"If the Americans have found a way to be able to do this then actually we should be doing it."
Footage of the savage execution of Henning - who was kidnapped last December in Syria - was posted on the internet by the group on Friday night.
Friends say Henning was never involved in politics or talked about current affairs or religion, and was a cheerful, happy personality, always eager to help others.
Kasim Jameel, from Bolton, who was also with Henning on the convoys and first interested him in helping the people of Syria, said he was "totally heartbroken."
"What can you say? When you lose someone so important to you, you can't put it into words," he said.
"Everyone that knew him from the convoys just can't stop crying, grown men with beards. We keep expecting him to come round the corner, and say, 'I was only joking'.
"He is the best of the best, a pure soul, he is in the best paradise. It's time for him to rest, he's done a lot of work, God's called an angel back."
Henning's wife Barbara had earlier this week pleaded for him to be freed.
"I ask Islamic State: please release him, we need him back home," she said.
"Some say wrong time, wrong place. Alan was volunteering with his Muslim friends to help the people of Syria. He was in the right place doing the right thing."
Mrs Henning revealed she had received an audio message of her husband pleading for his life, and had been told that a Sharia court had found him innocent of being a spy.
British Muslims have led condemnation of Henning's murder brandon it a "despicable and offensive act" which showed the Islamic State jihadists who killed him had "no regard for Islam".
Dr Shuja Shafi, Secretary General of the Muslim Council of Britain, said: "This reported murder is a despicable and offensive act, coming as it does on the eve of the Muslim festival of Eid Al-Adha.
"It is quite clear that the murderers of Alan Henning have no regard for Islam, or for the Muslims around the world who pleaded for his life.
"Alan was a friend of Muslims, and he will be mourned by Muslims."
The gruesome video of Henning's execution appears to show him dressed in orange and saying: "I am Alan Henning. Because of our Parliament's decision to attack the Islamic State, I, as a member of the British public, will now pay the price for that decision."
The killer, who speaks with a British accent and is believed to be the man responsible for the previous beheadings, then makes a direct statement to the Prime Minister: "The blood of David Haines was on your hands, Cameron. Alan Henning will also be slaughtered, but his blood is on the hands of the British Parliament."
The video then apparently shows the jihadist alongside an American hostage identified as Peter Kassig.
As the world reacted with shock to Henning's beheading, Prime minister David Cameron vowed to "hunt down" the terrorists responsible, French president Francois Hollande spoke of his "outrage" at the killing and US president Barack Obama condemned the "brutal murder".
The UN Security Council's president, Argentine Ambassador Maria Cristina Perceval, also sharply condemned the video, calling the killing a "heinous and cowardly murder."
Labour leader Ed Miliband described the killing as "appalling and barbaric".
Respect Party MP George Galloway described the killing as "a depraved Satanic act committed by devils in human form".
He wrote on Twitter: "It is a desecration of all that is holy."
Tory MP Mark Pritchard said: "If ISIS think the British people will be cowed they are gravely mistaken. For every act of brutality they birth greater national resilience."
And Labour's Fiona Mactaggart - who did not vote in last week's Commons decision to join US-led air strikes against IS positions in Iraq - said the murder made her question her decision.
"The vile murderers of ISIL make me almost wish I voted to bomb in Iraq last week. I want to avenge the death of Alan Hemming. I despise them," she said.
The UK will use "all the assets we have" to hunt down the Islamic State terrorists responsible for the "senseless" murder Cameron said today.
Speaking after meeting with intelligence and defence chiefs this morning, the Prime Minister said the killing of "a man of great peace, kindness and gentleness" showed that there was "no level of depravity to which they will not sink".