The murder of Alexander Litvinenko, the former Russian officer who died of radioactive poisoning on November 23, was, as the Foreign Secretary told the House of Commons yesterday, a horrifying and lingering death. It was a crime against a British citizen, a brazen attempt to silence a Kremlin critic and an assault on British laws and sovereignty by a suspect who appears to have had the clear backing, if not the active assistance, of the Russian Government itself. Moscow’s abrupt refusal, therefore, to consider the extradition of Alexei Lugovoy, a man against whom the police have gathered a wealth of scientific evidence, is not only “extremely disappointing”, as Mr Miliband told the House, it is also a calculated rebuff to a partner with whom Russia shares responsibility for global security, international law and the safeguarding of human rights.

Clearly, there had to be a response. Britain has already tried, repeatedly, to persuade the Kremlin to cooperate in the case. All it received was insults from President Putin, attempts to pin the murder on exiles in London and the parading of a constitutional ban on the extradition of Russian citizens. And with the linking of the case with Moscow’s demand for the return of Boris Berezovsky to face trial in Moscow, the confrontation has become overtly political. For both Gordon Brown and his new Foreign Secretary it was regarded as a test of their resolve.

Two things were clear. First, no step taken to demonstrate British anger would make the extradition of Mr Lugovoy more likely. And secondly, Russia would take retaliatory measures against Britain. Mr Miliband foresaw both in explaining to MPs why he had not sought the present impasse. Russia is vital in securing international agreements on Kosovo, Darfur, climate change and the fight against organised crime. Britain also has much at stake in its trade relations and cultural exchanges with Russia. All this, Mr Miliband conceded, was thrown into jeopardy by Moscow’s refusal to understand the gravity of the Litvinenko murder. And by detailing the trail left by the radioactive polonium210 and Mr Lugovoy’s movements in Britain, he implicitly admitted that this evidence is now unlikely to be put to Mr Lugovoy in a British court.

The key issue was what steps could be taken that were both measured and appropriate. Those announced yesterday were right. The expulsion of diplomats is a widely recognised way of conveying official displeasure, even if those declared personae non gratae themselves had nothing to do with the case. The target is the Russian Government, not the Russian people. Mr Miliband was also right to seek the arrest of Mr Lugovoy in any other country and to invoke the help of European allies in enforcing a warrant. Suspending negotiations to speed up visas is unfortunate, as this will hurt visitors. But such talks depend on mutual trust which is today clearly lacking.

Russia will certainly announce tit-for-tat measures. Given present Kremlin anger with the West – Russia has just announced withdrawal from an arms agreement – these may be more drastic. Britain will suffer, and cynics may argue that today’s measures are futile and counter-productive. But they send a signal to all those who would silence their critics abroad: Britain will protect those on its soil and cannot overlook murder for the sake of diplomatic convenience.