Theirs are the voices that go unheard, they say: Syrian exiles, many of whom escaped to Britain in the months after the suppression of peaceful protest by President Bashar al-Assad - the spark that led to civil war.
In a basement lecture hall in central London, a few dozen gathered, along with their British supporters, to review progress after more than four years of civil war.
On the platform was Amer Masri, who describes himself as Britain's first Syrian refugee.
He fled in 2011, just after he had been detained, tortured and told a guard had spat on the plate from which he was fed.
Opposition groups have gathered in Riyadh this week, trying to agree a common negotiating position.
Now that international players have begun to see the group that calls itself Islamic State (IS) as a greater threat than President Assad, the opposition is coming under pressure to abandon its implacable hostility to the Syrian government.
This is part of what is called the Vienna process, a path to peace being steered by Staffan de Mistura, the UN's special envoy to Syria.
Mouin Rabbani was Mr De Mistura's head of political affairs, but resigned in frustration at the glacial rate of progress.
He said David Cameron's talk of 70,000 Syrians ready to turn their fire on IS was unrealistic.
"In making that statement, the British prime minister was effectively saying that these would be the ground forces who would do the fighting… that rests on a fundamental misconception."
That sentiment was reflected at the London conference, where activists said misconceptions had arisen from an unwillingness to listen to Syrians themselves.
Muzna Al Naib, a film-maker, said the West should not ignore uncomfortable truths, for example that the Syrian government had killed many more civilians over the years than IS.
"You need to listen to us rather than taking your own narrative and talking on behalf of the Syrian people," she said.
"We are capable of organising ourselves, we are capable of running our own affairs, we are capable to fight our fight.
"So just stop the killing of civilians, take your human responsibility and don't claim to know more about Syria than Syrians."
She and others at this weekend's meeting were baffled that those who favour intervention, including Mr Cameron, now see the target as IS, not President Assad.
Mr Cameron is not just counting on bombing. Indeed, he has been explicit in arguing an aerial campaign will not be enough.
With both Western countries and Syria's neighbours unwilling to commit ground troops, a diplomatic resolution is the only option.
This week's meeting in Riyadh has been convened to get opposition groups to agree a united position for negotiations with the government in the New Year.
He was worried his mother and father, stuck in a town occupied by IS, could be endangered by British air strikes.
Corbyn's quote to Parliament:
"Yesterday, I was sent this message from a constituent of mine who comes from Syria, his name Abdulaziz Almashi, and I quote from his message.
"'I'm a Syrian from Manbij city, which is now controlled by Isil,' Abdulaziz writes.
"'Members of my family still live there, and Isil didn't kill them. My question to David Cameron is: 'Can you guarantee the safety of my family when your air forces drop bombs on my city?''
"It is a fair question from a family who are very concerned."
When we met, he told me that his parents had even felt a little safer when IS - called by some at the meeting by the longer acronym Isis - came, because then President Assad stopped bombing the town.
"There is a risk for their lives because Isis is there and you cannot trust Isis," he said.
"But, with the air strikes, now the risk has been doubled, because Isis, they don't have a uniform… they live with civilians and they look like civilians.
"The thing is how can the RAF distinguish between civilians and Isis?"
One of the most curious aspects of the rise of IS has been the unwillingness of the government in Syria to take it on.
President Assad's opponents say he encouraged the growth of IS, knowing he could then use the threat to convince the West he was the lesser of two evils.
Activists at last weekend's meetings in London told me the West was falling into a trap laid by President Assad.
Only by negotiating a real change in the government in Damascus, and not just a superficial change in the faces that front it, will the West convince these campaigners their cause has not been betrayed.
They will be a hard constituency to convince.
Shaun Ley presents The World This Weekend during December on BBC Radio 4, on Sundays at 13:00 GMT and afterwards on the iPlayer.