Lucas Torreira celebrates scoring Arsenal's fourth goal against Tottenham with his team-mates

Arsenal laid down a marker and leapfrogged Tottenham into the Premier League's top four with an outstanding display, their finest under manager Unai Emery, to deservedly win the north London derby at Emirates Stadium.

The Gunners' unbeaten run stretches to 19 games after the 4-2 win and this was their most significant of the season.

So how has Emery transformed Arsenal - and how far can they go?

Arsenal and Emery make biggest statement

As Arsenal's season kicked into gear in the weeks after their opening home loss to Manchester City and defeat at Chelsea in August, one question remained for manager Unai Emery and his players.

Yes, the winning run was very impressive - but how would Emery's bold, attacking style and fearless tactical approach fare when they faced their biggest rivals?

Arsenal produced evidence to suggest they could answer that question positively with an impressive performance in the 1-1 draw with Liverpool, when Emery's side refused to take a backward step.

This, however, was on another level and you could feel the renewed optimism on and off the pitch.

Spurs arrived at Emirates Stadium at the end of a testing week which saw them beat Chelsea, then overcome Inter Milan in the Champions League at Wembley.

Arsenal, albeit with a weakened team, were in Ukraine on Thursday but their energy, dynamism and potency was simply too much for Spurs, as Mauricio Pochettino's side suffered the rare experience of being overpowered.

Emirates Stadium was "more like a bearpit" on Sunday, says Phil McNulty

The Emirates is alive again after the toxic final Arsene Wenger months. The chants of "We've Got Our Arsenal Back" may be harsh on the former manager who achieved so much, but they carry meaning.

Emery has blown the winds of change through Arsenal like a hurricane. It is, quite simply, like watching a different team in a different stadium.

This place was accused, with justification, of being like a library in the past. This was more like a bearpit and how Emery's Arsenal revelled in it.

The demanding Spaniard insists on front-foot football and is a front-foot manager, a blur of perpetual motion on the touchline and a courageous strategist, as proved by his double half-time introduction of Alexandre Lacazette and Aaron Ramsey that gave Arsenal renewed impetus.

Arsenal have a genuine revivalist feel about them but needed big results and a big performance to back it up.

This was a win against their fiercest rivals that delivered on every level.

Emery injects steel into Arsenal

Arsenal's so-called soft centre was probed relentlessly under Wenger, with opponents believing they could profit from exerting their physical will on his teams.

Emery's Arsenal show resilience and steel in many forms, not least in stringing together an unbeaten 12-game league run despite not leading at half-time in any of those matches.

And here they picked up a physical and footballing momentum that ultimately Spurs could not cope with.

It was summed up in one sequence in the closing stages when Spurs, penned in their own corner, were subdued by a succession of shuddering challenges, much to the delight of Arsenal's fans.

Other statistics back up the growing belief there is a new toughness about Arsenal.

Arsenal last won a north London derby in the Premier League after trailing at half-time 11 years ago, while they have scored more goals in the second half (24) than any other side in the Premier League.

And it is a tribute to their determination and staying power that, if Premier League matches finished at half-time, Arsenal would be 19th in the table. How different it looks after 90 minutes.

Arsenal showed greater desire than Spurs. This, as well as the result, will be a source of huge satisfaction.

It all adds up to the surge of belief that swept around this stadium once Arsenal drew level and continued long after the final whistle.

Arsenal 4-2 Tottenham: Emery hails 'important' derby win

Can Arsenal stay in the top four?

Arsenal were 12 points adrift of Liverpool in fourth place last season, the Champions League places never seriously threatened.

They are in the top four now after this landmark win and they will have every right to believe they can be in the shake-up as the season goes on.

When Emery arrived, behind the scenes they might have settled for that as an opening campaign but the instant impact of his workaholic style and meticulous attention to detail has already elevated expectations.

Goalkeeper Bernd Leno still looks vulnerable on occasion, but elsewhere Arsenal have strength in all areas, coping comfortably here without Mesut Ozil after his latest back spasm.

Rob Holding is maturing in defence, while the signing of Lucas Torreira, looking a snip at £26m, has also re-invigorated Granit Xhaka.

It is the drive and positivity that impresses most and to top it off are two strikers who provide the "X Factor" that can change games.

Pierre-Emerick Aubameyang is a striker of the highest class and it was his brilliant, instinctive finish - struck instantly from the edge of the area - that restored equality after Spurs had led against the run of play at half-time.

He is the first player to score with 10 consecutive shots on target since Blackburn Rovers' Benni McCarthy in October 2007 and, since his debut, only Liverpool's Mo Salah has scored as many goals in the Premier League as Aubameyang's 20.

Emery is also finding ways to get his two most potent forces on the pitch together, with Lacazette playing his part with another goal, as he did to get a point against Liverpool. Big games. Big goals.

There will be stern tests ahead for an Arsenal side still in transition under Emery - but his body of work so far suggests the Gunners must consider themselves top-four contenders.