Richard Moore told the Aspen Security Forum that Russian intelligence services had struggled with a “toxic combination” of failing to getting an accurate picture of what was happening in Ukraine and a fear of “speaking truth to power” as the Russian president was unlikely to be pleased with what he was being told.

So, some of their information had been withheld from Mr Putin, he suggested.

Mr Moore, boss of Britain’s Secret Intelligence Service, said: “If I reflect on our Russian counterparts, like the Russian military, I don’t think they are having a great war.

“They clearly completely misunderstood Ukrainian nationalism.

“They completely under-estimated the degree of resistance that the Russian military would face.

“It was a toxic combination of them not really getting their intelligence right but also intelligence services reflect the societies they serve.

“I’m answerable to democratically-elected ministers, to parliamentarians, to judges over certain aspects of my work.”

Mr Moore, who is known as “C” as the head of the SIS, stressed how “different” it was to the “system” in Russia.

He explained further: “One thing that it does not pay is to speak truth to power.

“So, I suspect some of the reality of what they were about to encounter was just not being briefed up to Putin.”

He stressed that more than 400 Russian intelligence officers, which he said was around half of those across Europe operating under diplomatic cover, had been expelled.

“We reckon in the UK, that has probably reduced their ability to do their business, to spy for Russia in Europe, by half,” he added.

Spying by Britain and its allies had helped the West to counter the “false narratives” being pumped out by the Kremlin about the invasion which started on February 24, he said.

 next 12 months?

Some of the warnings by the western intelligence services had been met with a degree of “scepticism” which he said was understandable as keeping secret the source of the information, when shared, inevitably led to some “doubting Thomas” responses.

A small number of Russian “illegal” intelligence officers had been arrested, including a spy “masquerading” as a Spanish journalist trying to enter Ukraine as part of the Kremlin’s “destabilisation efforts” in the invaded country.

Mr Moore declined to comment directly on whether the invasion of Ukraine had led to a “target-rich environment” for the intelligence services to recruit people in Russia to spy for the West.

However, he added: “I very much hope that Russians, many of who will be within those intelligence services, within their diplomatic service, elsewhere in positions of influence inside Russia will reflect on what they are witnessing in the Ukraine.

“If I think back to the impact, for example, of the crushing of the Prague Spring, had in 1968. That was a moment when a number of Russians decided, Soviets in those days, that it was their time to try and strike back against the system that they were representing.”

On China, and whether the threat posed by it was being reassessed following its actions in Hong Kong and the supressession of the Uyghur people in the Xinjiang province, he said MI6 had “never had any illusions whatsoever about Communist China”.

He added: “There has been a growing recognition right across Government and our societies of some of the threats that the Chinese pose to our societies.

“We are putting more effort into China. We now devote more effort to China than any other single subject.

“It’s just moved past counter-terrorism in terms of our mission.

“That feels like a very big moment, post 9/11, post 7/7 in London. But it reflects the seriousness of the mission for us.”

He explained that MI6 was seeking to get “upstream” to deal with some of the threats posed by Beijing and to lift the lid of the “black box” of the Communist organisation, capabilities and tactical “intent” behind president Xi Jinping’s ambitions, partly given that the Chinese system is “still pretty opaque”.

“At one level, understanding Xi Jinping’s strategic intent is not difficult. If you read Made in China 2025, he lays out for you their ambitions around technology and their desires to dominate key technologies,” he said.

“But if you go beneath that strategy, in terms of how they implement, how they organise, what their tactical intent is, and then what are the capabilities they are building up, that’s a black box and there is a role for organisations like mine in helping British ministers and policymakers to understand that so they can navigate this really complex, difficult relationship with the Chinese.”

He also stressed that Xi Jinping was watching the situation in Ukraine “like a hawk”, which emphasied the need for the West to “tough it out” against Mr Putin’s invasion and continue supporting president Volodymyr Zelensky’s government and military during the winter so it can “win, at least negotiate from a position of significant strength,” so China does not see weakness which could lead it to “miscalculate” and invade Taiwan.

He explained that he did not believe that war was “inevitable at all” between the US, Britain, their allies and China.

“It’s really important that president Xi, as he calculates what he may or may not do on Taiwan, looks at what can go wrong with a misjudged invasion and we are seeing that played out. It’s important that we remind him of those risks and prepare accordingly,” he said.

Vladimir Putin’s spies ‘not having a great war’ over Ukraine, says MI6 chief Richard Moore