There are promises and promises, but we get nothing, Fatima, a refugee from Syria, told one of my colleagues in Lebanon last week. Her counterparts in Jordan where I was visiting tell a very similar story.

They call for more aid for those who have fled Syria of course – but also for something to be done for the millions left behind in their country’s vicious conflict.

Unless the world’s aid catches up with their spiralling numbers, the prospect for refugees will be grim. But it is inside Syria where children are dying from hunger in opposition-held areas, and where millions cannot reach the assistance and safety they need.

Gulf and Western governments have given more than $800 million to the UN’s appeals for Syria and its refugees this year, quite apart from millions more that is not so clearly recorded. The point is not that little has been given. The point is that it is being dramatically overtaken by the spiralling numbers who need it – within Syria and outside it – while so little progress is being made to reach those caught in the conflict.

When the new UN appeal comes out in late May – based on far greater numbers in need – the amount given so far will look alarmingly small. The need for more aid is vital and urgent. But it is also only the start. It is breaking down the obstacles that stop millions of Syrians reaching aid that is also absolutely vital. The scandal of 50 checkpoints – half government, half opposition – that stop aid convoys travelling from Damascus to Aleppo. The dwindling number of trucks that go through Turkey’s main crossing point at Kilis. That is the reality behind the shocking observation a few days ago, by the UN Emergency Relief Coordinator, Valerie Amos, that access to those in need is getting even worse.

From William Hague, the British Foreign Secretary, to Antonio Guterres, the UN High Commissioner for Refugees, many people label Syria the greatest humanitarian crisis of our time. Almost thirty years ago, there was little doubt it was Ethiopia, where hundreds of thousands faced famine – largely in the north of the country controlled by the rebel movements of Tigray and Eritrea.

The humanitarian answer then included two massive aid routes. With the agreement of Ethiopia’s government and rebels alike, Oxfam and Save the Children trucked vast amounts of relief from the south to the north, through the conflict’s frontlines. And with the acquiescence of all, Oxfam and others brought more over the border from Sudan, directly into opposition-controlled areas. Together, those routes saved, literally, countless thousands of lives.

Syria may or may not need exactly that answer. But it certainly needs the drive, the passionate refusal to take ‘no’ for an answer, and the determination to find ways round obstacles that characterised that aid effort then. Nothing less will do. Everyone with influence must make it clear to Syria’s government and opposition that they must do absolutely everything to allow aid to get through. The world – tragically divided over Syria so far – must unite in that call. The UN Security Council, with the authority only it has, must show that unity in action.