Within hours of airstrikes that killed at least 140 Yemenis attending a funeral on October 8, the Saudi-led coalition flatly denied any involvement. A week later, the Saudis threw up their hands and admitted responsibility. So how did this sudden U-turn come about?

The Saudis might be still clinging to their original position had it not been for a video (above) posted on the internet. Someone in Sanaa was filming the smoke from the scene of the attack when a second bomb struck – and the sound of a warplane could be heard screeching overhead. Later, fragments were recovered indicating that an American-supplied bomb had been used for at least one of the strikes.

The Saudis then said there would be an investigation – a move which, on past performance, did not inspire much confidence. On this occasion, though, the investigators' report arrived surprisingly quickly and despite being brief was surprisingly explicit (at least, by Saudi standards).

The report began by saying the attack was the result of false intelligence from a source linked to Abd Rabbu Mansour Hadi whom the Saudis regard as Yemen's legitimate president. The Saudis were allegedly told that "a gathering of armed Houthi leaders" was taking place.

The report does not say whether this intelligence made any mention of a funeral – in which case, even if "armed Houthi leaders" had been attending, many civilians were likely to be present as well. The size of the hall where the gathering was taking place – said to be one of the largest in Sanaa – should also have raised questions about what was going on inside.

The report says the Yemeni source "insisted that the location be targeted immediately as a legitimate military target" and adds:

"The Air Operations Center in Yemen directed a close air support mission to target the location without obtaining approval from the Coalition command to support legitimacy and without following the Coalition command’s precautionary measures to ensure that the location is not a civilian one that may not be targeted. A Coalition aircraft in the area carried out the mission ..."

This account may seem like a Saudi attempt to shunt some of the blame but so far there's no good reason to disbelieve it. It's obvious that the Saudis do make use of intelligence from Yemenis on the ground. The problem is that on this occasion the coalition did not evaluate the intelligence properly before acting upon it – which raises the question of how many times this has happened in the past.

Saudis have a history of attacks on civilians

The Saudis say their military are instructed "to exert all efforts to avoid civilians" but it's doubtful whether this is much observed in practice. The instruction seems to be mainly a response to pressure from the US and Britain – the kingdom's chief arms suppliers – who are more concerned than the Saudis about being seen to be implicated in breaches of international humanitarian law.

The Americans have been raising this with the Saudis for years – well before the current conflict in Yemen.

In 2009-2010 the Saudis were bombing Yemen in support of President Saleh (as he then was) in an earlier war against the Houthis. At a meeting with Prince Khaled bin Sultan, Saudi Arabia's assistant defence minister, the US ambassador in Riyadh raised concerns about attacks on civilian targets and showed the prince a satellite image of a Yemeni clinic that had been hit.

The prince's first reaction was to ask the Americans to supply him with more accurate weapons. His second reaction was to say that the clinic had been attacked because of "information received from Yemen that it was being used as an operational base by the Houthis".

According to the ambassador's note of the meeting, Prince Khaled elaborated on the problem of false intelligence and recalled an incident where President Saleh had tried to trick the Saudis into killing one of his political rivals by listing him as a target:

"There was one occasion when Saudi pilots aborted a strike, when they sensed something was wrong about the information they received from the Yemenis. 

"It turned out that the site recommended to be hit was the headquarters of General Ali Mohsen al-Ahmar, the Yemeni northern area military commander, who is regarded as a political opponent to President Saleh."

It appears from the funeral bombing that the Saudis have still not taken on board the lessons from 2009-2010 and there's also evidence that in the current war, as before, the Americans are again urging them to be more careful.

The American and British concerns in this area are not, of course, purely humanitarian. Civilian casualties make it harder to justify continuing to provide the Saudis with weapons and also undermine western policies elsewhere. Yesterday, for example, the Russia's UN ambassador asked – not unreasonably – why there should be a no-fly zone over Aleppo if there isn't one over Sanaa. 

It's not too far-fetched to suggest that the British and the Americans had a hand in the report about the funeral massacre. They were almost certainly given access to the military records and probably advised that confession, together with a credible explanation of what happened, would be a better course than obfuscation.

A day after the report appeared, the US, Britain and the UN's special envoy called for a ceasefire – which is obviously no coincidence. Earlier today, one Twitter user commented: 

"Ceasefires are used in Yemen to calm people down when publicity for Saudis gets bad."

Hopefully, that's too cynical a view. But we shall soon find out.