I began this article by describing Caruana as Italian, rather than Italian-American. This seems justified not so much because his mother Santina was born there before she moved to the US, but more because in 2005 Fabiano began to play under the Italian flag, winning its national championship on the three occasions he took part and also representing that country in international team events.

Yet although the family now lives in the Italian-speaking Swiss city of Lugano, Fabiano is not fluent in any language other than English-and he retains strong links to the US Chess Federation. At the end of his smashing victory in the Sinquefield Cup, he seemed even more than usually reserved-though as well-mannered as ever-when asked if he would restore his allegiance to the country of his birth: "I'd rather not say too much about that." That suggests to me that he may well do so. I would be surprised if the billionaire eponymous sponsor of that tournament, Rex Sinquefield, was not doing his best to give Caruana the necessary incentives.

I'm sure Fabiano, who seems an admirably level-headed and stable individual, will know what is best for himself. But I think it would be somehow fitting to have an Italian world chess champion, not just because the rules of chess that we now play emerged in that country during the Renaissance but also, of course, because of Nabokov.

Anyway, here is Caruana's victory in St Louis with the Black pieces against the current world champion. I suspect it is the last time Magnus Carlsen will treat his younger rival with anything less than the utmost respect. 1.e4 e5 2.Bc4 (Carlsen shows a little condescension: opening with the Bishop's Opening, an ancient line more often seen between beginners) Nf6 3.d3 c6 4.Nf3 d5 5.Bb3 Bb4+ 6.c3 Bd6 7.Bg5 dxe4 8.dxe4 h6 9.Bh4 Qe7 10.Nbd2 Nbd7 11.Bg3 Bc7 12. 0-0 Nh5! 13.h3 (This does not turn out well, but the apparently very strong 13.Nxe5 Nxe5 14.Qxh5 loses White's Queen to 14...Bg4 15.Qh4 g5) Nxg3 14.fxg3 Nc5! (Absolutely unafraid: Caruana feels no need to play safe by castling) 15.Bxf7+!? (Carlsen carries out his sacrificial threat) Kxf7! (After 15...Qxf7 16.Nxe5 White's attack really would be too strong) 16.Nxe5+ Kg8 17.Ng6 Qg5! (Cold-blooded calculation. Caruana could have simplified with 17...Qe8 18.Rf8+ Qxf8 19.Nxf8 Kxf8 but after 20.Qh5 Carlsen's active Queen would more than compensate for Black's notional superiority in material) 18.Rf8+ Kh7 19.Nxh8 Bg4! 20.Qf1 Nd3!? (Carlsen afterwards said he had missed this remarkable move: Caruana, with two pieces en prise, offers up a third. In fact it may be that 20...Be2 would have been even stronger). 21.Qxd3 Rxf8 22.hxg4 Qxg4! (In no hurry to capture Carlsen's Knight on h8. It's not going anywhere) 23.Nf3 Qxg3 24.e5+ Kxh8 25.e6? (This gives Caruana a clear path to the advantage: but only if he plays with the utmost precision) Bb6+ 26.Kh1 Qg4 27.Qd6 Rd8 28.Qe5 Rd5! (This, and only this, leads to a win) 29.Qb8+ Kh7 30.e7 Qh5+! (Not 30...Rh5+ 31.Nh2 and White is more than OK) 31.Nh2?? (Now this loses immediately. Carlsen had to play 31.Qh2 but the point of Caruana's manouevre would then be revealed by 31...Qe8 32.g4 Rd7 and with the advanced e-pawn doomed, Black should eventually win) Rd1+ 32.Rxd1 Qxd1+ 33.Nf1 Qxf1+ 34.Kh2 Qg1+ and Carlsen resigned. After 35.Kh3 Qe3+ and Qxe7 it's completely hopeless. The scale of the blunder by the world champion on move 31 is perhaps unique in his career: in the past it had always been his opponents who cracked under the pressure of relentless accuracy.