They were returning from a picnic when death rained down on their school bus.

At least twenty-nine children died, all of them under 15 years old. Among the wounded were another 30 youngsters.

In a war that has seen civilian targets repeatedly bombed including airstrikes on homes, markets and hospitals, Wednesday’s attack on a school bus in Yemen was yet another episode in what many now say is nothing less than a litany of war crimes.

Time and again journalists when writing about such atrocities in Yemen - this writer included – have referred to such strikes being carried out by forces that are part of a “Saudi-led coalition”.

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In itself such a description of the perpetrators is not inaccurate. But as my American colleague, Glenn Greenwald, pointed out a few days ago on Twitter, it does fail to ‘highlight the vital, indispensable, multi-layered support the US and UK have given’ this Saudi-led coalition from the very start of its bloody campaign in Yemen in 2015.

Best known for his role in a series of searing reports detailing the US and UK global surveillance programmes based on the Edward Snowden disclosures, Mr Greenwald, is on familiar territory when he makes such an observation and is right to say so.

It was almost two years ago now writing in the respected online news portal The Intercept, that Mr Greenwald highlighted the role UK military personnel have in overseeing airstrikes in Yemen.

While acknowledging remarks by the Saudi foreign minister that his staff had ultimate authority to choose targets, the article also quoted the minister admitting “British and American military officials are in the command and control centre for Saudi airstrikes on Yemen” and “have access to lists of targets.”

But it’s not just the presence of UK military personnel though that marks Britain’s complicity inhelping these breaches of humanitarian law in Yemen’s conflict.

The UK government’s own statistics speak also to materiel facts. Current data shows that that since the US and UK backed Saudi-led bombardment began in 2015, Britain has licensed £4.7 billion worth of arms to Saudi Arabia.

Among these are £2.7 billion worth of what is known as ML10 licences for the likes of aircraft, helicopters and drones. It has also licensed £1.9 billion worth of ML4 licences that cover grenades, bombs and missiles, some of which have been used to bomb civilian targets and possibly even the school bus on Wednesday, during the airstrike in Yemen’s northern province of Saada.

While all this carnage might be taking place far away, here in the UK we have known for some time that many of these weapons originate on our doorstep. Some are manufactured at the Glenrothes plant in Fife run by Raytheon the third biggest arms company in the world, which accounts for 95% of its total business from arms sales.

“Many of the bombs are being made in Scotland, with Raytheon's factories playing a central role in the destruction,” Andrew Smith of Campaign Against Arms Trade (CAAT) told The Herald yesterday.

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It was back in 2014 that the Raytheon deal for the Paveway IV missile was announced and estimated to be worth around £150 million. Right from the start the buyer was believed to Saudi Arabia.

This was confirmed shortly after in the defence press, with the contract reported to have been approximately £150 million for 2,400 units, in the order of £62k each.

By 2015 Raytheon announced that all its UK manufacturing would be moving to Glenrothes.

Around this time too there was criticism of then SNP business minister Fergus Ewing, who visited the Raytheon Glenrothes plant, despite his party publically condemning the war and UK government role in arms deal to Riyadh.

The following year in a detailed report entitled, ‘Bombing Businesses’ which looked at the effect of airstrikes on Yemen’s civilian economic structure, the US based Human Rights Watch (HRW), was able to link the use of Paveway IV missiles to attacks on civilian infrastructure.

At six of the sites visited as part of its field research HRW identified four munitions that the US produced or supplied and two the UK produced or supplied including a Paveway IV guided bomb produced in May 2015, after the start of the coalition’s aerial campaign. Since then UK arms sales to Saudi Arabia have grown.

“It is long past time for Theresa May and her colleagues to end their uncritical political and military support for this awful regime,” insisted Andrew Smith CAAT spokesperson speaking in the wake of the school bus strike on Wednesday.

“The Scottish government has rightly criticised these arms sales, and we hope that it is using its influence to pressure Westminster to end the arms sales," Mr Smith continued.

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On that very issue the SNP’s Foreign Affairs spokesperson, Stephen Gethins MP, yesterday described the strike on the school bus in Yemen as marking “the latest stain in the conflict, as well as on the UK’s foreign policy record.”

If the UK aims to be a serious partner for peace, Mr Gethins insisted, then it must end fuelling the conflict with billion of pounds worth of arms, and instead hold the Saudi regime to account.

“The UK is not a mere bystander in that war, it is an active player. Despite the mounting evidence of breaches in international law, the UK government is still content on looking the other way, whilst simultaneously supplying arms and military advice to the Saudi government,” Mr Gethins accused.

Last month a cross party committee of MPs concluded that the time has now come for a new inspection regime to be implemented to check how British arms exports are being used.

Among the recommendations were that better monitoring would help the Government decide whether to grant export licences “as well as addressing questions around compliance and enforcement”. It also suggested stronger controls on arms dealers.

While the recommendations were welcomed by anti-arms trade campaigners they like many others, are under no illusions that deeds not just words from the UK government are what matters right now. Without such speedy action, countless more Yemeni civilians will undoubtedly suffer the fate of those aboard the school bus in Saada on Wednesday.