Theresa May's response to Russia's involvement in the attack on ex-spy Sergei Skripal is measured but significant, according to experts.
The measures announced by the Prime Minister include the expulsion of 23 suspected Russian spies from the country's embassy in the UK, which Royal United Services Institute (Rusi)'s deputy director general Professor Malcolm Chalmers said was "very significant".
But he said the Government had appeared to try to strike a balancing act so as not to escalate the situation further.
Prof Chalmers said: "The expulsion of 23 diplomats is a very significant number.
"There are 58 Russian diplomats in their embassy now accredited on the diplomatic list - that's a high proportion of the Russian presence.
"I think everybody expects a reciprocal act in the other direction in relation to the UK presence in Moscow.
"The Government has tried a balancing act between measures which are so small as to be seen as insufficient proportionate to the very considerable crossing of red lines that this attempted assassination involves, on the one hand.
"But on the other hand not being so large in nature as to risk further escalation.
"This is more than a token response.
"It's measured but significant, I would say."
But Prof Chalmers added: "None of the measures which the Prime Minister announced today will have any impact on Russian economic performance."
He suggested the Kremlin's motive may have been to isolate the UK from its allies, including the US, Germany and France, but that it appeared their response was "relatively positive" so far.
And he added: "The coverage in Russia, while all the state media are denying it, they are doing that in parallel with a lot of statements in terms of 'this is what happens to people who betray their homeland' and things of this nature - there's a fake news element going on."
His colleague, Dr Jonathan Eyal, Rusi's international director, said he expected a stronger reaction from Mrs May but he thought there may be further statements and escalation from the Government depending on how President Vladimir Putin reacts.
And he said the Kremlin's actions could be the "new normal".
"From the Russian perspective, tearing up the rulebooks, making themselves unpredictable, being able to get at us just below the threshold of war is the strategy for the future," Dr Eyal said.
"So what you see now is very much the new normal rather than the exception.
"And again it will not only apply to the UK although it particularly applies to the UK perhaps because in the last few months, the UK for a variety of reasons has led in the siren calls about the potential Russia threat and therefore slapping the Brits across the face may have been a useful moment for Mr Putin."
And he dismissed the idea that the attack could have been carried out by a "rogue" operative.
Dr Eyal said: "I don't buy that for a second.
"There's plenty of intelligence services in Russia and plenty of them are competing with each other but quite frankly the implications of this attack and chances of being found out are so high and the target who was being assassinated was so low that is inconceivable that someone in Moscow could have taken the decision to do this operation and risk the anger of Mr Putin without having the cover.
"The idea this was a rogue element within the Russian intelligence is quite frankly not very credible."
"It is an odd operation because the target itself doesn't look particularly valuable but the implications are quite serious or could be serious for Russia.
"I think there is an element of deterrence - let's be honest, you can dispatch a person with a bullet to the head, you do not need to go into baroque performances with chemical agents.
"You do it in order to show that you can do it."
Asked why now, he said: "My argument would be now is just as good as any time. I don't think it's connected to the (Russian) election."