After nine unsuccessful attempts and a wait of almost six years, United finally progressed in the world's oldest competition courtesy of a five-goal demolition of Northampton Town and earned a second-round visit to non-League minnows Histon.

Leeds – and hat-trick hero Jermaine Beckford, in particular – put the boot into the Cobblers in merciless fashion to seal a first FA Cup win since a fifth-round defeat of Crystal Palace in February 2003 under Terry Venables.

A surprise last night was the inclusion of Malcolm Christie in the starting line-up. The 29-year-old striker has been without a club since being released by Middlesbrough in the summer of 2007 and a couple of unsuccessful trials at Hull City and Leeds, the latter brought to an abrupt end by a back injury.

However, after spending the past two months building his fitness and then impressing in a reserve team outing and two behind-closed doors friendlies, Christie had clearly done enough to persuade Gary McAllister to give him a chance.

He showed enough promise without doing anything spectacular to suggest the former England Under-21 international could have a role to play in the push for promotion from League One.

Beckford, meanwhile, notched a second hat-trick of the season after being restored to the side as one of six changes. He started the rout on 13 minutes after David Prutton had flicked a towering clearance from Lubomir Michalik into his path and he fired an unstoppable right-foot shot past Frank Fielding in the home goal.

After the disappointment of Saturday's last-gasp derby defeat to Huddersfield Town, it was just the fillip Leeds needed and they doubled their advantage in the 28th minute when Jonny Howson's shot was deflected past the Northampton goalkeeper by Mark Hughes. Four minutes before the break Fielding somehow allowed Ben Parker's shot from 35 yards to squirm under him on the line.

The highlight of Northampton's night followed when Jason Crowe met a left-wing corner sweetly to beat David Lucas in the 44th minute, but Beckford netted his second during stoppage time.

Northampton's misery continued after the break with the outstanding Neil Kilkenny playing Beckford through on 55 minutes and the striker showed terrific composure to score his hat-trick goal.

Leeds, who were so in control that Fabian Delph was able to stay on the bench and, therefore, remain fresh for a potential England Under-21s debut at Bramall Lane tonight, did concede in the final minute when Crowe met another corner sweetly but it could not detract from a fine night for McAllister's men.

Northampton Town: Fielding; Crowe, Hughes, Dolman, Jackman; Guttridge, Gilligan, Davis, Holt (Bignall 52); Constantine (Henderson 71), McGleish. Unused substitutes: Dunn, Dyer, Benjamin, Jones, Taylor.

Leeds United: Lucas; hughes, Michalik, Telfer (Webb 76), Parker; Kilkenny, Douglas, Prutton, Howson; Christie (Showunmi 71), Beckford (Becchio 71). Unused substitutes: Delph, Ankergren, Robinson, Snodgrass.

Referee: P Crossley (Kent).