The leader of a superpower with his finger on the nuclear button has been diagnosed as a “reckless narcissist” by a Scots psychologist.

No, it’s not President Donald Trump – it’s Russian president Vladimir Putin, the man Trump once described as a “strong leader”.

However, Scots neuroscientist and clinical psychologist Dr Ian Robertson has analysed the behaviour of Putin and diagnosed him as a reckless narcissist who has an overestimation of his own judgement.

Robertson, who is professor of psychology at Trinity College, Dublin has written several books about the human psyche, including The Winner Effect, which examines how power affects the brain.

Robertson picked out several examples of Putin’s conduct and concluded he should be feared by world leaders, particularly UK Prime Minister Theresa May. The professor said the use of nerve agent novichok to target ex-spy Sergei Skripal and his daughter Yulia indicates “utter contempt” for May.

The Kremlin continues to deny responsibility for the attack in Salisbury and President Putin said last week “the man would have died on the spot” if military-grade poison had been used.

Robertson, a graduate of the University of Glasgow, said: “The poisoning of the Skripals shows Putin has utter contempt for what he sees as a weak and untrustworthy country and leadership. He had a great bond with Tony Blair – and may even have aspired to emulate him – but the Iraq adventure destroyed that.”

Robertson said the war in Iraq, military intervention in Libya and the potential for eastern expansion of NATO “rankles” with Putin, who won an expected victory in the presidential election in March with a 76.7 per cent share of the vote. The main opposition leader, Alexei Navalny, was barred from the race.

Robertson said: “Power has made Putin reckless, greedy and narcissistic, with an overestimation of his own judgment and a lowered self-awareness – these are all common symptoms of the effects of extreme power on the human brain.”

Three quarters of Russian voters backed him because he is perceived to be focused on the “redemption of what is seen as a national humiliation since the collapse of the Soviet Union,” according to Robertson.

“It seems that many Russians care more about the regaining of national greatness than they do about the bad state of their economy,” he said. “Many – maybe the majority – of Russians feel he has made them feel better about themselves.

“Also, he embodies the strongman, authoritarian father-figure that seems to figure strongly in Russian history, Russian thinking and some recent philosophy.”

Robertson cited three examples which he says give an insight into the Russian president’s psyche.

He said: “In June 2005 Putin saw a diamond-studded Superbowl ring on the finger of New England Patriot’s owner Robert Kraft during a US business visit to St Petersburg. He asked to see it, tried it on, and said “I could kill someone with this”. He then, allegedly, put it in his pocket and abruptly left the room.

“Three months later, while visiting the Guggenheim Museum in New York, he was shown a glass replica of a Kalashnikov gun filled with vodka. According to one biographer, Putin nodded to one of his guards, who, to the astonishment of all present, simply pocketed the piece.

“And at an EU council meeting in Russia in Sochi in 2007, knowing that (German Chancellor) Angela Merkel was terrified of dogs, he brought an enormous black dog into the room with her. He is ruthless with a cruel streak.”

Merkel was visibly shaken as the dog sniffed around her. Putin sat back in his chair and smirked.

Robertson said this ruthlessness with a cruel streak is one of many reasons foreign leaders should fear him and pointed to the assassination of ex-secret service agent Alexander Litvinenko in London.

“The reckless use of military-grade biological weapons and radioactive materials for assassinations show that for sure he should be feared,” said Robertson. “He presented an award to the person believed to be responsible for using polonium to poison Litvinenko (Andrey Lugovoy) and that person is now an MP in the Russian parliament.”

Putin was brought up “in very tough circumstances” in St Petersburg, which was known as Leningrad when the 65-year-old was a child. Robertson said: “He was a street fighting youth who joined the KGB in 1975 and had a strong loyalty to the Soviet Union. He showed physical courage in East Germany when the KGB post in Dresden was mobbed by crowds in 1989 when the Berlin Wall fell, and he saw them off single-handedly.”

He reportedly used a pistol to fend off looters and was able to burn files to prevent them being seized. It’s this fierce nationalism which endears him to Russians and strikes fear in enemies, according to Robertson.

Putin has annexed Crimea and taken advantage of instability in Ukraine and Syria to advance his interests. “With any luck, in future he will focus on trying to improve the way of life of Russia’s people and may feel less obliged to engage in nationalistic external manoeuvres and adventures,” said Robertson. “However, he is a nationalist and does care about his country. He may seek yet another term in power, in which case he may have to start beating the nationalist drum again which may well result in more military posturing and adventures.”

The Winner Effect – How Power Affects Your Brain by Professor Ian Robertson is published by Bloomsbury.

PUTIN’S MOST DISTURBING COMMENTS

“The task of the government is not only to pour honey into a cup, but sometimes to give bitter medicine.”

“I am not a woman, so I don't have bad days.”

“I am the wealthiest man, not just in Europe, but in the whole world. I collect emotions.”

“Sometimes it is necessary to be lonely in order to prove that you are right.”

“I don’t read books by people who have betrayed the Motherland.”

“Hitler wanted to destroy Russia - everyone needs to remember how that ended.”

“Sanctions are unpleasant, but mostly for those who introduced them.”

“We will chase terrorists everywhere. If in an airport, then in the airport. So if we find them in the toilet, excuse me, we’ll rub them out in the outhouse. And that’s it, case closed.”

WHAT OTHERS SAY ABOUT PUTIN

“Putin, having accidentally received enormous power into his hands, administered it to catastrophic consequences for Russia… he, having accidentally scrambled to the top, is now a king and a god, whom everybody should worship and fear.”

Murdered Russian journalist Anna Politkovskaya

“Putin is only 65. The bad news is, I don't know when and how his rule ends. But the good news is, he also doesn't know that.”

Former chess champion and Russian exile Garry Kasparov

“He might be bad, he might be good. But he’s a strong leader.”

President Donald Trump