But Town were made to work hard for their victory by a fired-up Lions side who hit the post in the second half and wasted several chances.

Crowe smashed in from close range after Adebayo Akinfenwa had stepped over Liam Davis' sweeping cross from the left byline in the 16th minute.

Town should have been ahead in the game earlier than that, with Ryan Gilligan first firing a shot wide and then sliding a rebound from Akinfenwa's shot later in the move into the outside of the post.

The visitors were good value for their lead until Millwall began to grow in confidence later in the half, with Lewis Grabban hitting a couple of shots off target when well positioned.

But neither attempt troubled Mark Bunn, and the Cobblers went in leading 1-0.

The home side continued where they left off after the interval, with substitute Tresor Kandol getting a good connection but dreadful direction on one back-post header after only a couple of minutes.

Grabban continued to be a thorn in the Cobblers' side, and showed instant control and good strength to hold off Danny Jackman on 53, but Bunn was equal to his powerful shot in what will go down as a good save.

On 73 minutes Chris Hackett showed his speed to leave Jackman for dead and spear in a cross which Kandol headed wide and moments later Grabban rattled the post with a curling effort from fully 30 yards.

But the visitors held on to book their place in the second round.

Millwall: Forde, Frampton, Whitbread, Alexander (Kandol 46), Grabban, Hackett, Craig, Martin, Fuseini, Laird, Abdou (Brkovic 46). Subs not used: Edwards, Dunne, Harris, Smith, Forbes

Cobblers: Bunn; Gyepes, Hughes, Doig; Crowe, Guttridge (Coke 59), Gilligan (Osman 59), Jackman, Davis; Akinfenwa, Constantine (Holt 76). Subs not used: Larkin, Henderson, Dunn, Dolman

Attendance: 3,525

Away fans: 237