Can Boris Johnson do anything to deter Russia's Vladimir Putin from taking over Ukraine?

Right now Boris Johnson is in a room on his own writing a speech that he will deliver to the nation later this morning in which he will declare this invasion "a catastrophe for the continent".

The prime minister is focusing on this address after an emergency Cobra meeting in which he, Foreign Secretary Elizabeth Truss, Defence Secretary Ben Wallace and others discussed ramping up of sanctions.

Sources tell me he wants to put in place the "largest and most severe sanctions package" ever against Russia - something he will discuss with G7 leaders in a meeting this afternoon.

They say he wants that to be agreed across all countries but if not, he would still be minded for the UK to act at that level.

That said, the government has been heavily criticised for its sanctions earlier this week, even while admitting intelligence pointed to what we're seeing today - a full invasion.

Sanctioning three individuals and five banks, according to the Conservative chair of the Foreign Affairs Select Committee Tom Tugendhat, was weak, and didn't just fail to deter Vladimir Putin, but even encourage him.

Others contrasted the UK's action to Germany- normally accused of being dovish - but taking the huge step of placing the Nord Stream 2 gas pipeline on hold.

Britain's power over Russia is focused on the amount of money in London- sometimes called "Londongrad" linked to Russian elite- including with links to the Kremlin and to corruption.

But it's not just the level of sanctions that may leave Russians sanguine about them - but something else as well.

The Atlantic Council point out that we already had 200 sanctions against Russia before any of this - including 144 against Ukraine. They say there is a risk of "sanctions inflation" where each on is worth less.

In fact, polling from the Levada Centre that shows when Russians were asked if they were worried about Western economic sanctions in 2014, the majority said they were quite worried.

When they same question was asked in December 2021 - a big majority said they weren't.

Estimates suggest that the 2014 sanctions did hit the Russian economy but perhaps not as much as a falling oil price. Estimates suggest overall the hit was 0.2% of Russian GDP each year until 2018.

So to be effective now would require a massive ramping up. Not just of economic sanctions but ones that hit Putin politically.

Tom Maybe from the Chatham House think tank told me they have to hit "Londongrad" as much as the Russian economy.

But even with a huge increase in sanctions, will it be enough?

Whitehall insiders and Russia experts tell me that to know what Putin is thinking, normally you just have to listen to what he says.

Or read what he writes. Like in a 5,000 essay last year when, going by the Kremlin's translation, he insisted that Russians and Ukrainians were one people and that he was becoming more convinced "that Kyiv does not need Donbas".

He added: "I am confident true sovereignty for Ukraine is possible only in partnership with Russia."