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General Sir Richard Shirreff, the former British officer who was Nato’s deputy supreme allied commander, told the Today programme this morning the possibility of the war in Ukraine leading to military conflict between Britain and Russia could not be ruled out. Asked if this was possible, he replied:

Absolutely there is a possibility that we as a nation could be at war with Russia, because if Russia puts one bootstep across Nato territory, we are all at war with Russia. Every single one, every single member of the Nato alliance.

Article 5 [of the Nato alliance] says an attack on one is an attack on all, so we need to change our mindset fundamentally, and that is why I say our defence starts in the UK on the frontiers of Nato.

What became evident in the days leading up to this invasion is that Vladimir Putin is increasingly isolated. That bizarre video of him berating his senior officials shows that he’s making these decisions increasingly in isolation and illogically.

And unfortunately I think that that is part of the reason why the initial round of international sanctions that [were] put in place by ourselves, by France, Germany, the US, Canada and others, didn’t have the deterrent effect.

The sanctions package that will be put in response to this is already actually having an effect. Just the announcement that it’s coming - we’ve seen the Russian stock market, the equivalent of the FTSE, drop by over 30%. That is a huge reduction in Russia’s economic abilities to fund this invasion.

And those sanctions will be laid today and over forthcoming days to really prevent Russia from funding this invasion.