With 12 rounds complete and just Saturday’s and Sunday’s final two rounds to come, the Candidates in Toronto could hardly be closer. Three players share the lead, another is just half a point behind. The €500k tournament will decide which of its eight contestants challenges China’s Ding Liren for his world crown later this year.

Leaders after 12 rounds (of 14) were : Ian Nepomniachtchi (Russia), Hikaru Nakamura (US), and Gukesh Dommaraju (India) all 7.5; Fabiano Caruana (US) 7; Praggnanandhaa Rameshbabu (India) 6. Three others follow. Key games to come are: Saturday’s round 13, Nepomniachtchi v Nakamura; Sunday’s round 14, Nakamura v Gukesh and Caruana v Nepomniachtchi.

Nepomniachtchi, who won the 2020-21 and 2022 Candidates, holds the unique record of having led, alone or jointly, in all 40 rounds of the three events. If the 33-year-old can complete the job and qualify for a third world title match, it would be a remarkable achievement.

This time his margin of superiority has been slimmer than when he outpaced the field two years ago, but he remains the only unbeaten player. A 67-move marathon, during which Vidit Gujrathi missed wins at moves 34 and 37, kept him in front. A feature of Nepomniachtchi’s success has been his reliance on his trusty Petroff Defence 1 e4 e5 2 Nf3 Nf6 as Black, which all his opponents have failed to defeat or have avoided.

Nakamura, the world No 3 and a popular streamer, joined the leaders with a late surge of three successive wins. The fast-talking American has incredible energy. This week he used the rest day between his victories to score his 69th first place in Titled Tuesday, the giant weekly chess.com event open to all titled players, which regularly attracts 500 or more entries.

Nakamura had lagged behind Nepomniachtchi and Gukesh for most of the Candidates, due to two costly defeats against Vidit. Then he hit a purple patch and scored victories in rounds 10, 11 and 12 against the tailender, Nijat Abasov, the 18-year-oldPraggnanandhaa, and France’s gifted but erratic Alireza Firouzja.

Gukesh, only 17 years old, has been the revelation of the Candidates, and is now in serious contention to become the youngest world champion in chess history, a record held by Garry Kasparov at age 22. He has excelled in complex positions at Toronto, and his best win featured his queen and rook infiltrating White’s queen’s side before his mating attack against the white king on the other flank.

The teenager had been considered an outsider due to his youth and his unstable performances in the months leading up to the event. At the London Classic in December, he finished third behind England’s Michael Adams. In Toronto his only loss has been an unlucky one against Firouzja, where his subsequent despair was captured on video.

Caruana, 31, the world No 2, was the pre-tournament favourite, but lacked sharpness at critical moments in the early rounds, and lost an important game to Nakamura in round eight. The US champion, who won the 2017 Candidates and went on to draw all 12 games with Magnus Carlsen for the world title which the Norwegian star abdicated last year, recovered his best form in the second half at Toronto, including an impressive strategic win against Firouzja. It is still a tall order for Caruana to pass or catch all three rivals ahead of him.

The race is exceptionally close, and will very likely go to the 14th and final round on Sunday, or even to speed tie-breaks on Monday. Nepomniachtchi has the hardest pairings, meeting Nakamura and Caruana in the final two rounds. Games start at 7.30pm BST on all days, and there is free and live coverage with grandmaster and computer commentaries on major chess websites as well as on the official channel.

The women’s world championship has been a Chinese monopoly since 2017, and is likely to remain so. With two rounds left in the women’s Candidates at Toronto, the Chinese pair have it between them in the race to find a challenger to the world title holder, Ju Wenjun. Tan Zhongyi leads with 8/12, ahead of Lei Tingjie 7.5, Aleksandra Goryachkina and Kateryna Lagno (both Russia) and Koneru Humpy (India) 6. Three other women trail behind.

Tan scored the fastest win of the tournament in round nine when Vaishali Rameshbabu (India) blundered into defeat in just 21 moves. The opening is well worth a look as Tan secured easy equality with an unusual counter to the 2 c3 Sicilian, which is popular in English club chess and online games.

3916: 1 b4+! Kc4 (if Kd6/d5 2 Nb5+) 2 Qe2+! Kc3 (if Kd5 3 Qe6+ Kd4 4 Qe3+ and 5 Qxa7) 3 Qe3+ Kc4 (if Kb2 4 Qb3+ Ka1 5 Nc2 mate) 4 Qb3+ Kxd4 5 Qe3+ and 6 Qxa7.