Jack Wilshere scored four minutes from time as Arsenal reached the fourth round of the FA Cup with a 1-0 victory over Swansea in their replay at the Emirates Stadium.
A stubborn Welsh rearguard was finally broken when Olivier Giroud teed up the England midfielder whose drive from 20 yards was past the impressive Michel Vorm in a flash.
It maintains Arsene Wenger’s proud record of never losing in the FA Cup third round and the Gunners will travel to Brighton and Hove Albion in the last 32.
Wilshere's goal came from Arsenal's 26th attempt in the game and they were forced to be patient against Michael Laudrup’s side, who won 2-0 in the Premier League match in North London.
Michu, the two-goal hero in December’s encounter, was on the bench and he watched a low-key first-half short of goalmouth incident.
The closest either side came to breaking the deadlock was when Wayne Routledge’s cross from the left found Kyle Bartley but the former Gunners trainee saw his header come back off the crossbar.
For Arsenal, Thomas Vermaelen’s scuffed effort from eight yards was saved by the legs of Vorm with almost the last kick of the opening period but they improved considerably after the break.
Swansea have made more clearances off the line than any other team in the Premier League this season with eight and they made two more to stay on level terms.
Wilshere's shot was palmed in the air by Vorm and fell to Walcott whose effort from no more than four yards was blocked on the line by the chest of Danny Graham.
Frantic appeals for a penalty were correctly waved away by referee Mark Clattenburg and from the resulting corner, Leon Britton nodded Vermaelen’s header off the line.
Walcott, who earlier held off Chico Flores and dinked an effort over Vorm only to watch it trickle past the far post, should have done better after cutting inside the Spanish centre-back in the penalty area but failed to hit the target.
And he was even more culpable when he found himself unmarked in the penalty area but failed to make any contact on Bacary Sagna’s cross and the cross came back off the far post.
Laudrup did bring on talisman Michu for the last 20 minutes but the defence that held firm, despite absent captain Ashley Williams, for so long was finally broken on 86 minutes.
Giroud, who had a poor evening and was profligate in front of goal, provided a deft touch for man-of-the-match Wilshere to blast home an unstoppable shot and send the Arsenal faithful home with something to cheer after a freezing evening at the Emirates.
MAN OF THE MATCH
Jack Wilshere - Arsenal: Energetic performance from the midfielder in an advanced role behind the strikers which was capped by the winning goal.
Arsenal: Szczesny 6; Sagna 7, Vermaelen 6, Mertesacker 6, Gibbs 6; Diaby 6, Coquelin 7, Wilshere 8, Cazorla 6; Giroud 5 Walcott 7. Subs: Ramsey N/A
Manchester City: Vorm 7; Richards 6, Bartley 6, Chico 7, Tiendalli 6; Britton 6, Agustien 5, De Guzman 5; Dyer 5, Routledge 5, Graham 6. Subs: Ki 6, Pablo 5, Michu 5.