Mathieu Flamini proved to be Arsenal's unlikely derby hero as his double sealed a 2-1 victory over Tottenham in the League Cup third round.
Flamini opened the scoring in the 26th minute, pouncing on Michel Vorm's save to fire home from close range, as the Gunners edged a largely poor first half.
Harry Kane had the ball in the net early in the second period only to be denied by the offside flag, but Calum Chambers turned Nacer Chadli's cross into his own net to level the scores.
Kane's brilliant volley almost put Spurs ahead before Olivier Giroud wasted a great chance of his own, but Flamini's superb second secured the victory for the visitors.
Joel Campbell made his first competitive start for Arsenal since January 4 and he missed the first clear chance of the game, heading over the crossbar from close range after Giroud had failed to connect properly with Kieran Gibbs' cross.
Both sides lacked quality in the final third during a scrappy opening 25 minutes but Arsene Wenger's side silenced the vociferous home support just short of the half-hour mark. Vorm could only parry Alex Oxlade-Chamberlain's shot back out into the six-yard box, and Flamini arrived to drive the rebound into the roof of the net.
Danny Rose dragged a shot into the side-netting but Spurs were being wasteful with the ball, and Campbell had half a chance to double Arsenal's lead as he just failed to connect with Giroud's cross.
Kane dragged a left-footed effort narrowly past the far post and then the England striker found the back of the net shortly after the break, but the offside flag was raised following Christian Eriksen's parried effort.
Tottenham were firmly in the ascendancy by this point and they found the equaliser after 56 minutes, as Chambers stuck out a leg and diverted the ball past the helpless David Ospina following Chadli's low cross from the left.
Kane thought he had put Spurs ahead with a stunning scissor-kick volley but Gibbs superbly headed clear on the line, before Giroud failed to squeeze the ball past Vorm when played in by Aaron Ramsey's fine pass.
But, just as the game appeared to be heading for extra time, Flamini struck again. The Frenchman rifled a superbly controlled volley into the bottom corner after finding space on the edge of the box.
White Hart Lane was stunned and, though Spurs piled forward in the closing minutes, Arsenal held on to reach round four.
