Russia and the DPR clearly don't want to have to put this guy down, as the story implicitly admits in the first sentence:

British national Aiden Aslin has been told by his Russian captors that his execution will go ahead and that 'time is running out' for Britain to save him.

Otherwise they'd just announce that this guy was done-zo and take him out back. So that brings up my favorite part:

... the [British] Government has thus far refused to intervene directly to prevent the sentence.

They want this guy dead, of course, a martyr for their Neo-Imperialist cause. I'm sure they pray to Satan for it to be televised live. Then they can decry the pitiless brutality of the aggressor and trumpet the righteousness of their cause.

Oh, and they don't have time to intervene, anyway. Way too busy shipping weapons into a war zone. For peace.