The senior cyberspy for Britain reiterated on Tuesday that any discussion of using such weapons was extremely risky and that Britain would expect to see clues if Russia was beginning to consider using its nuclear arsenal in its conflict with Ukraine.
Jeremy Fleming, director of the GCHQ surveillance agency, told BBC Radio that Russia was running low on supplies of troops, allies, and ammunition after more than seven months of fighting.
According to Fleming, Russian President Vladimir Putin has so far adhered to long-standing military doctrine that forbids the use of nuclear weapons, but his agency will be on the lookout for any indications that this could change.
“I would hope that we will see indicators if they started to go down that path,” he said, without saying what those indicators could be.
“But let’s be really clear about that, if they are considering that, that would be a catastrophe in the way that many people have talked about”.
Fleming also said he was sure Putin was worried about the dangers of escalation and that might be a sign of why “he has not reached for these other forms of waging war”.
In a speech due to be delivered later on Tuesday, Fleming will also say that Russians were beginning to understand the desperate situation Moscow is in over the conflict.
“They’re seeing just how badly Putin has misjudged the situation,” he will say, according to excerpts from his speech.
“They’re fleeing the draft, realising they can no longer travel. They know their access to modern technologies and external influences will be drastically restricted. And they are feeling the extent of the dreadful human cost of his war of choice.”