Until now, the Foreign Office has been reluctant to blame the government of its ally President Paul Kagame (pictured below) for the surge in fighting in the east of the Democratic Republic of Congo.
This week two things changed. First, the M23 rebels, who are backed by Rwanda, seized the town of Goma. Then the UN came out with a report which alleges not only that Rwanda supports M23, but that its minister of defence, James Kabarebe, actually commands them.
"We judge the overall body of evidence of Rwandan involvement with M23 in the DRC to be credible and compelling.
"We will be studying the implications of this report in full, but these allegations will necessarily be a key factor in future aid decisions to the government of Rwanda," said a statement signed by Foreign Secretary William Hague and Development Secretary Justine Greening.
It's a big departure. In a much criticised decision, the former Development Secretary Andrew Mitchell signed off on £8m in aid to Rwanda on the last day of his tenure at the department. A further £21m due in December now looks in doubt.
Rwanda has grown at 7 per cent per year for the last decade and DFID loves the government's efficiency.  "By 2020, the government of Rwanda aims to complete the country's transformation from a poor, post-conflict nation to a thriving, middle income, regional trade and investment hub," says the DFID website.
"Rwanda uses aid very well, both in terms of the results it achieves and accounting for its use."
All of which is true, but Rwanda's success is partly built on DR Congo's failure. The Rwandan exchequer benefits from minerals which have been illegally mined in DRC and smuggled over the border.
After Hutus who had taken part in the genocide of Tutsis in 1994 fled into Kivu, the Rwandan Patriotic Front government has seen the eastern DRC as its legitimate zone of influence, and a security buffer. "The de facto annexation of north Kivu is well underway," said an international aid official in Goma.
The Rwandan government says the UN has a campaign against them, which started when UN troops failed to stop the genocide of 1994. They accuse their accusers of bad faith or bias, and deny all involvement with M23. The west, they say, is to blame for what's happening in Congo. But now even Rwandans who support the RPF are beginning to ask questions.
"I tired of defending arrests of journalists, of jailing opposition leaders because you disagree with them," wrote Rama Isibo, a Rwandan journalist who has always supported the government. "I tired of defending our right to attack Congo, knowing the millions who suffer as a result.
"I tired of explaining to my western expat friends why no independent opinions were allowed on public media. I tired of explaining that fear that is unspoken, the looking over your shoulder when you speak."
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