Magnus Carlsen’s next defence of his world crown will be a 12-game series in London from 9-28 November 2018. The decision, already widely rumoured, was formally announced at an Evening Standard co-hosted function in London on Wednesday.

George Osborne made the announcement and Carlsen, who turned 27 on Thursday, also spoke, in excellent English but with a jest way too subtle for the many non-chessplayers present. The Norwegian said that he hoped to become the first world champion to win a title match game in London since 1993. That was when Garry Kasparov defeated Nigel Short, the joke being that Kasparov later lost his title to Vlad Kramnik in London during 2000 without winning a game.

The actual venue has yet to be announced although the organisers say they have several short-listed options. The prize fund is the world body Fide’s minimum of $1m, which could yet present a problem if Fabiano Caruana wins the eight-man candidates in Berlin in March. In that case the billionaire Rex Sinquefield, who has made his home city of St Louis into a global chess capital and who could easily fund a much larger purse, may try to have the match switched to the US.

Marketing the challenger in London will not be easy, anyway. The candidates favourite is Levon Aronian, and although chess fans would relish a Carlsen v Aronian series, Norway v Armenia can hardly excite a wider public. The best result in Berlin for the organisers would be a victory for one of Americans, Caruana or Wesley So, while the worst would be if Shakhriyar Mamedyarov from Azerbaijan triumphed.

Watching the games online is likely to be a controversial issue, since Fide’s commercial partner Agon intends to try to repeat its monopoly over publication of game moves during play, which caused ill-feeling and legal actions at the last title match in New York 2016.

Meanwhile, the 10-player annual London Classic, which has both Carlsen and Aronian in the field, is under way this weekend at the Olympia Conference Centre. The event is also the final leg of the Grand Chess Tour, whose previous rounds were in France, Belgium, and the US, while the eight-player British Knockout Championship, with Short as No1 seed, had its quarter-finals on Friday.

Norway has two world champions now after Aryan Tari won the world junior (under-20) crown on tiebreak from an Armenian and an Indian. India’s 12-year-old prodigy Rameshbabu Praggnanandhaa tied for fourth, unbeaten on 8/11. He scored a grandmaster result and still has three months to achieve two further GM norms and so break Sergey Karjakin’s age record as the youngest GM at 12 years seven months. But Praggnanandhaa could yet rue failing to convert some promising positions in the last few rounds, including a pawn up against Tari.

Tari’s fastest win was scored in daring style after his provocative 4…Bg6 opening choice where 4…Bd7 is usual to prevent 5 e6. Later 9…g5!? took the initiative,and was rewarded with the passive 13 Be3? (13 Nxe4 dxe4 14 c3 is safe). Tari’s vigorous 15…e5! set up complications where his opponent missed the winning tactical trick 21…Qxg5! with a potential knight fork, and White soon resigned faced with a lost endgame.

Grigoriy Oparin v AryanTari

1 e4 c6 2 d4 d5 3 e5 Bf5 4 g4 Bg6!? 5 e6 Qd6 6 exf7+ Bxf7 7 f4 Nf6 8 Nc3 Nbd7 9 Bh3 g5!? 10 fxg5 Ne4 11 Nge2 Bg7 12 O-O O-O 13 Be3? Nb6 14 Bf4 Nxc3 15 bxc3 e5! 16 Bg3 Nc4 17 Rf5 Bg6 18 Qd3 Qe7 19 dxe5 Nxe5 20 Qe3? Bxf5 21 gxf5 Qxg5! 22 Nf4 Rae8 23 Qe2 Ng6 24 Ne6 Nf4 25 Qg4 Nxh3+ 26 Qxh3 Qxf5 0-1

3523 1...Rxh3! 2 gxh3 Qxe4+! 3 Rxe4 Nf6! and White resigned. The threat Bxe4+ forcing mate is so strong that White must give up queen and rook by 4 Qf4 Nxe4 5 Qf3 Nd6, emerging a piece down in the ending.