A former head of British spy agency MI6 says Russia cannot maintain its invasion of Ukraine.
Sir Richard Dearlove told 7.30, "there's no way that Russia, over time, can sustain a war in a country which is the size of France and part of Germany put together, with a population the size of Spain".
"Even if militarily [Mr] Putin manages to bombard the cities into submission, that the Russians then take control, he's going to be facing an insurgency, which probably would be resupplied from the West.
"Even an army of — people have estimated 600,000 — couldn't hold the country down. So it's just hard to see where this goes except into an absolute area of destruction and a downward spiral, both for Ukraine and ultimately for Russia too."
On Tuesday, Reuters reported Mr Putin said on television that Russia will not use any conscript soldiers in Ukraine "and there will be no additional call-up of reservists".
Sir Richard said the war "could last weeks, if not months, and it will be difficult to see how [Mr] Putin can sustain that".
"We've seen with the capture of the first city [Kherson] … The Russians are in control of it but that's about all," he said.
"There isn't any submission, and it could just go from bad to worse."
He said he could not see the situation "doing anything but deteriorating really seriously into an even bigger crisis than it is at the moment".
"A lot of rubble, a lot of civilian casualties. It's catastrophic."
Sir Richard was head of MI6 from 1999 to 2004, having begun his service as a spy there in 1966.
Attempt to destroy morale 'not working out'
Former Ukrainian deputy defence minister Alina Frolova concurred with Sir Richard's outlook.
She said Russia was trying to create as much "devastation" as possible to destroy the Ukrainians' morale.
"Which is not working out, weirdly. We became more, much stronger," she said.
Her greatest fear now is not conventional weapons but tactical nuclear weapons.
"Obviously they are losing, so he is in quite [a] tough position. And he needs to prove that he's strong enough," Ms Frolova said.
French President Emmanuel Macron called Mr Putin on Sunday to seek assurances about the safety of Ukraine's nuclear facilities.
Questions about Putin's calculus
Questions have been repeatedly raised about Mr Putin's motives. Some senior Western political figures are suggesting he has a mental health issue.
Current vice-chair of the US Senate Intelligence Committee, Senator Marco Rubio, suggested last week that Mr Putin had a "neurological" condition, backing that up just days ago by telling CNN: "It's not a curiosity, it's not to mock him or troll him, it's because he may be willing to take steps now that the old Vladimir Putin would not."
Several years ago it was suggested Mr Putin had the early stages of Parkinson's disease.
"That led to a group of one or two very distinguished neurologists examining very carefully all the recent tapes of Putin being interviewed," Sir Richard said.
"The suggestion that's come out of that, which is being taken pretty seriously in the UK, but of course it is speculative, is that there are clear signs, possibly of Parkinson's.
"I don't understand the detailed medical analysis, but I know that two symptoms, one is loss of restraint, and the other is psychosis.
"And then there's a third factor, which is Putin's appearance, which indicates that he might well be on steroids.
"That is, I gather, one of the standard treatments if you have got Parkinson's, which is pretty worrying.
"I mean, if we're dealing with someone who isn't behaving rationally because of a medical condition. But I don't think we can do more than speculate on that at the moment."
The Kremlin has rejected the claim of Parkinson's as untrue. The Kremlin also rejected claims Mr Putin may have cancer.
Kremlin intelligence vital
Getting a better take on what is going on is vital to world leaders attempting to coerce or cajole Mr Putin into ending the conflict.
"Sources inside the Kremlin, they have existed historically from time to time, the most famous probably being Oleg Penkovsky during the Cuba crisis [in 1962]," Sir Richard said.
"I very much hope that either my service or CIA does have that level of penetration. That's the best we can hope for. I mean, this is the moment when you need an explanation."
But even if the Ukraine invasion goes badly, Mr Putin may stay in power, he added.
"If you're familiar with the Kremlin, and the way that that functions, there's a very, very tight group around [Mr] Putin. I don't think he's going to be easily deposed," he said.
"Unless General Valery Gerasimov, the chief of the general staff, suddenly were to say, 'This is too much, that guy's out of control'. But I think this is unlikely."
Wake-up call for the west
As hundreds of thousands of Ukrainians flee to safety from their homes, Europe is still reeling from the shock of a war on their doorstep.
"We have to draw some really fundamental conclusions from this," Sir Richard said.
"It's a wake-up call for all of us in terms of our national security policies, on defence policies, on issues to do with government spending, energy security in particular, the speed at which we go to zero carbon and green policies. It affects a whole range of issues.
"We've lulled ourselves into a false sense of security. And I think, in particular, I'm deeply critical of the European continental powers that have allowed themselves to become energy-dependent on Russia.
"The cost of that, historically, it's going to be very, very high."
