For so long this had looked like being Arsène Wenger's nightmare: first half good; second half not so good. Arsenal had entered the new year on top of the table after an excellent opening 19 Premier League matches and they had been consistently good throughout 2013. The last thing the manager wanted was a stuttering start to the season's second half.

But Arsenal got there in the end. Cardiff had defended for each other, showing their discipline, and they had refused to wilt in the face of mounting pressure. Yet Arsenal had the hero in Nicklas Bendtner, who appeared as a second-half substitute to provide the decisive moment.

The cameo was underpinned by drama. From Nacho Monreal's cross, Bacary Sagna forced the Cardiff goalkeeper David Marshall into a save but Bendtner was on hand to lash the rebound high into the net. He promptly fell on Marshall, turned his ankle and was forced off. As he limped round the fringes of the pitch, he was afforded a gladiator's reception. The same crowd had booed him in the Capital One Cup against Chelsea on 29 October. Bendtner will be out for weeks, rather than days, according to Wenger.

Theo Walcott gave the scoreline a more presentable look with the second, a lovely chip over Marshall from the outstanding Jack Wilshere's flick, and Arsenal could exhale, as they jumped back to the summit. It was tight but they deserved it.

Cardiff gave their all, even if their offensive ambition was limited, but the action for them came in the directors' box, where Vincent Tan sat alongside Ole Gunnar Solskjaer, the man he has wooed into becoming his new manager. He whispered into Solskjaer's ear and the most fun to be had during a boring first half was to guess what particular pearls of tactical wisdom he was imparting. Solskjaer looked suitably engaged.

Arsenal made a meal of their task, particularly in the first half when, Wilshere apart, they had no tempo to their play. There was an impression that not only those in the stands were contending with hangovers. Arsenal's passing was frequently careless.

Cardiff were compact, keen to protect rather than push, neat and tidy without quickening the pulse. Their wide midfielders dropped deep and there was chuntering from the home crowd about Marshall's perceived time-wasting as early as the 20th minute. The goalkeeper was eventually booked for the offence, on the hour.

They created precious few chances, with Jordan Mutch's 27th-minute effort on the counter-attack standing out. He escaped Laurent Koscielny's attentions to get his shot away from a tight angle but Wojciech Szczesny saved. At 2-0 Szczesny blocked from the captain, Steven Caulker, at close quarters.

Arsenal dominated in territorial terms and Wilshere worked to inject urgency but the end product was erratic. Walcott had three first-half efforts but none of them troubled Marshall, while Lukas Podolski, playing at centre-forward in place of the injured Olivier Giroud, struggled to make an impression.

He dropped deep in search of the ball, which did little to advance his candidacy as the leader of the line, and his performance was rather summed up when he got in the way of a goal-bound Santi Cazorla shot. He was replaced by Bendtner.

Wilshere had appealed for a penalty on 25 minutes after Gary Medel's challenge, while Cardiff felt aggrieved when Craig Noone's cross early in the second half clearly struck Monreal's hand on the very edge of the area. The officials were unmoved. Walcott later felt that Ben Turner had gone into the back of him inside the box. Turner and Caulker gave towering displays in central defence.

The second half was more impassioned as the home crowd came to confront the possibility of costly dropped points. Wilshere embossed his status as the game's most eye-catching player when he wriggled through to explode a shot off the outside of the near post before Per Mertesacker fluffed two glorious chances.

The first one was the howler and everybody connected to Arsenal did howl, especially the big German. Mertesacker was completely unmarked from Walcott's cross but he headed past the post. Minutes later, again unmarked, he rose to nod Walcott's corner off the outside of the post. Again he sank to his knees in disbelief.

Arsenal camped inside the Cardiff half and, when Caulker cleared Sagna's header off the line in the 83rd minute and Marshall then denied the substitute Tomas Rosicky, it seemed the visitors would hold out. Bendtner had other ideas.