Club Player Successfully Navigates 15 Moves of Theory Before Collapsing into Panic at Move 16

The prepared line stops on move 15, printed in bold on a sheet folded to pocket size, and the ruled line beneath it is where Thursday's game actually began.

The match was Division Three, 90 minutes plus a 30-second increment, played in Room B at the Lower Third, a space booked in two-hour blocks and shared that evening with people who had other plans. White opened 1.e4 e5, a C50 Italian he files under "reliable," and reached move 15 at a mean of 26 seconds a move, the time it takes to recognise a position rather than read one. His opponent, who had prepared four, spent the same fifteen catching up.

Move 16 is where the score sheet goes quiet. He wrote nothing, then wrote something, then wrote over it. The clock transcript shows 14 minutes and 11 seconds on a single move against a per-move median of 40 seconds, and by move 24 he had 31 of his 90 minutes left while the boards either side of him had already stopped their clocks.

Dalia's Denominator. Method: 63 score sheets collected from Room B across five evenings. Unit: one move. A move counts as prepared only if it appears in the mover's own printed file, not a book, not a video, his file. I can confirm 44 of the 63 games reached the end of a file; two sheets were illegible, so read that as 44 plus or minus two. Uncertainty: a file records what a player can print, not what he knows.

Within those 44 games, the largest single clock charge landed within two moves of the end of a file 31 times. Median charge: 11 minutes 40 seconds. The consequence is not an evaluation. It is a player reaching move 43 with 40 seconds, a rook endgame he had drawn twice since April, and a flag that fell with four minutes left on the room's block, which is what he told the arbiter: he was fine until move 16.

A reply on the club's message board gives the position after 16 to two decimals and adds that it is fine. The figure comes from Stockfish 17 at depth 24 on a laptop that was also running a spreadsheet. It is accurate, it is version-bound, and it is not a plan.

"A prepared move is a move on a sheet you can produce," said Inez Gable of the standards board. "Everything after move 15 is play, and play is rated."

The three games in my sample whose files ran past move 25 produced no charge above five minutes. I cannot separate deep files from strong players; the two arrive bundled and 44 games will not unbundle them. The club's opening-book collector has read the number as proof anyway.

The endgame teacher, who has spent two years saying games are decided in endings, watched the flag fall and repeated himself.

Tessa Fenn lives with a player who files openings by coloured tab and has become an accidental expert in what not to say. "Don't tell him the position is fine," she said. "The position is fine. That was never the problem."

Basil Holloway prints the files to order at his counter, and says the most common request of the week after a league night is the same opening, deeper: four more bold lines.

His new file runs to move 22. The extra seven are printed in the same bold as the first fifteen, which is a formatting choice rather than a promise, and on Thursday they will be read once, at 26 seconds each, before the ruled line.