Arsenal secured another weekend at the top of the Premier League with a 3-1 win over Tottenham in the North London derby.
For an even first half, Thomas Partey's stunning free-kick from outside the box was cancelled out by a Harry Kane goal.
However, Arsenal pulled away in the second period, scoring either side of a red card shown to Spurs defender Emerson Royal by referee Anthony Taylor.
Mistakes are punished in derby games, and on Saturday, Tottenham let the occasion get to them.
Hugo Lloris' blunder gifted Gabriel Jesus a goal in the 49th minute, and Arsenal never looked back.
It was a physical match, with both teams guilty of unfair play and generally getting away with it until Emerson Royal was sent off for a challenge on Gabriel Martinelli.
It was a rash tactical foul, with Emerson going in quite high, the kind of prototypical "orange card" offence that sometimes results in a red card but usually results in a yellow card.
Taylor's rope, on the other hand, had worn out. It is always the player's responsibility to avoid giving a referee a decision to make in these situations.
Arsenal demonstrated to Spurs why it is critical not to make stupid mistakes. Arsenal would only need four minutes to make Tottenham pay.