Luton substitute Adam Watkins was the star of the show as he scored five minutes after coming on to send the Blue Square Bet Premier side through to the FA Cup second round 1-0 at the expense of Northampton
League Two Northampton were left to rue a number of early second-half misses as Luton squeezed through to the next round by the narrowest of margins.
This feisty derby had everything apart from goals in the first-half with two Luton penalty claims turned down and a disallowed goal for the visitors.
Luton skipper George Pilkington was guilty of wasting the best chance when he somehow headed Ashley Westwood's free-kick wide from six yards.
The Hatters' first penalty shout came after 10 minutes when Michael Jacobs left a leg dangling, while 20 minutes later referee Andy D'Urso also turned down a shove on Amari Morgan-Smith.
Northampton responded and Adebayo Akinfenwa might have opened the scoring in the 20th minutes, but his header was brilliantly saved by Kevin Pilkington.
The Cobblers' on-loan West Brom star Saido Berahino swept home only for the strike to be ruled out for offside.
After 64 minutes the lively Berahino showed his class for Luton, turning sharply before bringing a great reaction save out of Sam Walker with a delightful chip.
Northampton's John Kissock then somehow headed over from a corner unmarked six-yards out.
The Hatters were sensing their chance and began to build the pressure at the other end.
And with 10 minutes to play it was a half-chance taken with aplomb that won the tie for Luton.
Watkins reacted to a loose ball and buried a ferocious left footed effort low into the corner from the edge of the box.
Northampton rallied bravely and still managed to carve out a few chances in the closing minutes, Michael Jacob's and Akinfenwa coming close but it proved to be in vain.