World chess champion Magnus Carlsen of Norway and US challenger Fabiano Caruana concluded a seven-hour, 115-move draw in the first of their 12 scheduled games in central London today.
The 27-year-old Carlsen was close to becoming the first world champion to win the opening game of a World Chess Championship as black in 37 years until a blunder on move 40 made a draw the most likely result.
Three hours later it came to pass, with Carlsen the only player with the possibility of winning, and Caruana successfully prevented such an outcome.
Since taking the title off India's Viswanathan Anand in 2013, aged 22, Carlsen has successfully defended it twice.
Caruana, 26, earned his title match - which is taking place amid Victorian trappings in The College, Holborn - by winning the eight-strong Candidates Tournament, a double round-robin event that took place in Berlin earlier this year, where he finished with nine points, one ahead of Azerbaijan's Shakhriyar Mamedyarov and the last runner-up Sergey Karjakin of Russia.
The 12-game match is organised by the World Chess Federation and is offering €1 million (£877,000/$1.14 million) in prize money.
Caruana's 17th move was seen by experienced observers as a blunder, putting him behind on position as well as on the clock, and leaving Carlsen to go for a win with the disadvantageous black pieces.
When one player has made a move, they stop their clock and time starts running for their opponent.
If a player does not make the required number of moves within each specified time-frame, they forfeit the match unless their opponent has insufficient material to checkmate with, in which case it is a draw.
Before things got serious there had been a moment of awkward comedy at the opening of the match as Hollywood actor Woody Harrelson, charged with making the ceremonial first move on behalf of Caruana, accidentally knocked over the white king.
To compound matters, Harrelson then misheard the American player's instruction and played his white queen's pawn forward rather than his king's pawn - much to the amusement of the defending champion and the spectators watching on the other side of a giant glass screen.
Meanwhile at the Women's Chess Championship tournament in the Russian city of Khanty-Mansiysk, China's defending champion Ju Wenjun closed in on a place in the quarter-finals.
The 27-year-old from Shanghai, who took the title from fellow Chinese player Tan Zhongyi in May, has established a 1-0 lead over 48th-ranked compatriot Zhai Mo and needs only a draw in their second game to advance.
In a tournament that has already delivered numerous surprises - with Tan and second-seeded Indian player Humpy Koneru already out - another is in prospect in the match between Russia's ninth-ranked Valentina Gunina and 40th-ranked Uzbekistan player Gulrukhbegim Tokhirjonova.
The latter player, who beat Tan in the previous round on a deciding tiebreaker, leads 1-0.
The form-book is steadier in the match between Ukraine's fourth-ranked Anna Muzychuk and 13th-seeded Antoaneta Stefanova of Belarus, with the Ukrainian one up.
Meanwhile Koneru's conquerer, 31st-ranked Jolanta Zawadzka of Poland, is 1-0 up against 15th ranked Zhansaya Abdumalik of Kazakhstan.