Sir John Sawers, ex-MI6 chief, warns of Russia 'danger'
Russia has become a danger to Britain and the country must be prepared to take steps to defend itself and its allies, the former head of MI6 says.
Sir John Sawers, who recently retired after five years as chief of the Secret Intelligence Service, told BBC Radio 4's Today programme that Russia poses a "state to state threat".
Sir John said dealing with such threats would require more defence spending.
But he called on issues with Russia to be addressed by "increased dialogue".
He said he was disappointed how, after the end of the Cold War, Russia's and Europe's paths had failed to converge.
Russia's threat was "not necessarily directly to the UK but to countries around its periphery".
"[Russia] keep on reminding us that they have nuclear weapons," he said.
"The one level in which Russia and America are equals is at the nuclear level.
"Now we don't want to have a repeat of the Cuban missile crisis in 1962 where we got to the brink of nuclear war.
"We need to be able to address this through increased dialogue."
His comments come after a year of fighting in eastern Ukraine between government forces and pro-Russian separatists.
"We shouldn't kid ourselves that Russia is on a path to democracy because it isn't," Sir John said.
"One of the aspects of the modern world is that we live in a much more dangerous world these days.
"The stability that we had during the Cold War, or the predominance of the West that we had in the decade or two after the Cold War - that is now changing.
"It's a much sort of flatter world, a much more multi-polar world and there are real dangers associated with that."
Sir John described Russia as always having been an "issue of concern" for security services.
"Europe and Russia are not converging with one another so we're going to have to find a new way to coexist with Russia," he said.
"This crisis at the moment - it's focused on Ukraine but Ukraine is a symptom. It's not the real problem.
"The real problem is how we live with a Russia which feels very exposed. Putin's actions are ones of a leader who believes his own security is at stake.
"And here we've got nuclear bombers approaching the Cornish coast."
Sir John said the UK needed to prepare to take defensive measures for itself and the nation's allies, which include the Baltic states and central Europe.
"We've got to have the capability to deal with things like the hybrid warfare that we've seen Russia deploy, first in Crimea and then in the Donbass region, we've got to have the ability to deal with cyberwarfare.
"What's really important is that we're able to fulfil all of our defence commitments and I think that that's going to require a reversal in the trend in defence spending.
"We're going to have to spend more on our defence and our security because the threats are greater."
In a wide-ranging interview, Sir John also discussed the threat from jihadists.
His comments come after Mohammed Emwazi, a Kuwaiti-born British man in his mid-20s and from west London, was identified as "Jihadi John", an individual pictured in the videos of several beheadings of Western hostages.
Sir John said there were two answers to the question of why people became radicalised.
The first is that Muslims "are less well integrated" into UK society "and there are a number of social and economic factors that are related to that".
Secondly, he said, the Islamic religion "as a whole is not well geared to reviving and modernising itself so that it meets the values and the norms of a 21st Century society".
"So there's a big political challenge which can only really be taken up by leaders in the Islamic world... it can't be imposed by the West."