UK officials have been accusing Russia all week of being behind a poisoning in Salisbury, presenting it as a “chemical weapons attack.” There is a decided lack of evidence that Russia actually was involved in the incident, and Russia denies having anything to do with it.

Still, tensions keep rising, and Britain keeps doubling down. On Friday, Foreign Secretary Boris Johnson said not only was it Russia, but it was “overwhelmingly likely” that Russian President Vladimir Putin “personally” ordered the attack.

Russian officials, already increasingly mad about the allegations, issued a statement following Johnson’s declaration calling it “shocking.” They further labeled it “an unforgivable breach of diplomatic etiquette.”

British officials have invested heavily in portraying the poisoning as a Russian plot, and have stuck to that despite unwillingness to present evidence backing up that claim. Russian officials say they were willing to help in the investigation, but Britain clearly is uninterested in that.