Chess: Find the world champion’s surprise winning move

England’s hopes of a top 10 finish at the 163-nation online Olympiad were dashed at the weekend despite a notable victory against the highly rated Armenians. Heavy defeats against Croatia and Bulgaria meant that England finished only sixth in their group, from which the top three qualified for this week's knock-out stages.  

England’s women were predicted to be the weak link, but they gave a solid performance. Costly dropped points came from where it was least expected, the experienced top pair of Michael Adams and Luke McShane, while the England juniors struggled against higher-rated opponents. 

Russia dominated the group and seem likely to reach the final, with China their probable opponents. The third chess super-power, the United States, is without their top pair of the world No2 Fabiano Caruana and the US champion Hikaru Nakamura. 

Nakamura’s epic online match with Magnus Carlsen concluded last week after 38 games with the world champion winning controversially. It was an Armageddon game, where a draw on the board counts as a win for Black on the scoreboard. Carlsen established a fortress defence of rook, bishop and pawn which Nakamura's king could not penetrate. 

Next month the online action moves to St Louis, where Garry Kasparov, still the all-time No1 for many fans,  will play random chess against Carlsen, Caruana and Nakamura.

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Gideon Stahlberg v Alexander Alekhine, Hamburg 1930.  Can you work out the then world champion's move as Black which persuaded his opponent to resign immediately?

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