If chess is the gymnasium of the mind, as it was once dubbed by Blaise Pascal, the recently-concluded 2018 World Championship match in London witnessed 20 days of intense work-outs of the grey matters and an extraordinary amount of mental muscle-flexing for the coveted crown.

It took 15 games, 773 moves and 51 hours of fierce fighting over the board as Magnus Carlsen, epitomizing the iconic Bobby Fischer quote, crushed his opponent Fabiano Caruana's mind to take home a cool cash prize of 550,000 euros (486,000 British pounds) and, more importantly bagged his fourth straight world championship crown. Just two days before his 28th birthday, the Norwegian mastermind underlined his status as, arguably, the greatest sportsperson to make the move on the 64 squares since the supercomputers and the gigabyte processors came out of the high-profile and ground-breaking science and technology research organizations and highly-restricted and top-secret defense labs to the dressing rooms of world sports.

In today's computer-aided chess world, light years ahead of those unbelievable days of mental mathematics of Jose Raul Capablanca, Alexander Alekhine, Mikhail Botvinnik, Mikhail Tal among a slew of brilliant brains, the young man from the land of polar explorers and sea expeditionists have traversed a long way through the black and white chequered board in pursuit of greatness.

Since dethroning Vishy Anand, arguably the best in the business in the post-Kasparov era, in the Indian's own backyard in 2013, a self-effacing Carlsen has been an undisputed four-time world champion.

After his cliff-hanger win in the rapid tie-breaker in London, when asked about his favorite chess player, the reticent Norwegian, born with a prodigious talent, unabashedly replied: "Probably myself, three or four years ago."

However, Carlsen's unusual and unlikely ultra-defensive approach during the all-drawn 12 game contest – a first in the competition's 132-year history – had brought him under fire.

His erstwhile mentor, Gary Kasparov, came down heavily on the ski-loving Norwegian, "In light of this shocking draw offer from Magnus in a superior position with more time, I reconsider my evaluation of him being the favorite in rapids. Tiebreaks require tremendous nerves and he seems to be losing his."

Another of Carlsen's former world champion predecessors Vladimir Kramnik too came down heavily on the current world champion for his lack of killer instinct during the crucial 12th game which could have sealed the title even before the rapid tie-breaker.

"It could have been a fantastic great match with a lot of tension. If Magnus had been in a more fighting mood it could have been one of the greatest matches ever in chess," Kramnik rued during his analysis for www.chessbase.com.

He also mentioned: "I cannot imagine him doing this a few years ago."

One of the famous Polgar sisters, Susan, was particularly harsh on Twitter as she posted: "This has to change! @FIDE_chess needs to change this rule! No draw offer should be allowed! There is no draw offer in tennis, ping pong, boxing, MMA & other sports. Fighting draw is no problem. But not because one's nerves is shot! Am I wrong?"

However, an unassuming Carlsen, whose 2014 peak rating of 2882 is still the highest in history, made amends in the rapid tie-breaker to hold his ice cold nerves.

The losing finalist, Caruana, conceded in the post-game interview: "I think the results show that he is the strongest player in the world… and he is the World Champion, so it's quite fitting."

Kasparov's reaction to his protégé's win on Twitter was: "Congratulations to @MagnusCarlsen, World Champion once more! Valiant fight from Caruana pushed Magnus to show his best, and, unfortunately for Caruana, today he did!"

Meanwhile, five-time former world champion Anand, who was knocked off the perch by Carlsen in 2013, when asked about the inevitable GOAT question by sports website ESPN, came out with a subtle reply: "I thought Carlsen had (made an attempt to settle this question) before. He'd done all the hard bits earlier – record rating and years without a single tournament he didn't win. I thought he needed to pad it up a bit… dot the I's and cross the T's kind of thing and that would have been a very good argument. I don't know if he exactly clinched it here but it's one more world title which should pad it up nicely."