Andy Scott and Phil Gray, two strikers who were brought to the Manor Ground by Joe Kinnear, combined to grab the goal which will probably end up dragging Kinnear down into the third division with his old club Oxford.
Darren Patterson closes down Liam George during last night's 1-1 draw
United fans had ironically cheered the fact that it had taken 77 minutes for their team to manage a shot at goal with chants of "one shot to the Oxford boys", when an overhead kick by Gray was pounced on by Scott.
The former Brentford forward reacted quickly to nip behind his marker and poke a shot over the line before goalkeeper Nathan Abbey could reach it.
It was a real poacher's goal and one which United had been building towards as they controlled the second half of last night's Division 2 match at Kenilworth Road.
They went behind on 18 minutes when centre back Julian Watts had the simplest of tasks in toe-poking home a right-wing corner from Matthew Taylor.
It was a poor goal for the U's to concede, with Watts allowed to attack space just six yards from United's line.
The visitors were fortunate not to find themselves further behind at the interval.
Luton's central midfielders Paul McLaren and Matthew Spring were frequently running through the middle to set up attacks, and United were on the back foot for most of the first half.
Goalkeeper Richard Knight came to their rescue several times. He pushed away an outswinging Steve Howard cross in the third minute and did well to tip over an improvised mid-air shot from McLaren which led to the corner from which the Hatters scored.
And just before the break, Knight showed excellent reactions to turn another goalbound drive from McLaren over the bar.
United manager David Kemp had begun with the team that finished against Oldham, with Paul Powell in for Joey Beauchamp. Matt Murphy started because Robert Quinn was still injured.
Apart from the neat promptings of Paul Tait in midfield, though, the visitors looked completely out of it in a one-sided first 45 minutes.
Tait had to go off two minutes before half-time with a recurrence of last week's leg injury, and he was replaced by Peter Fear, who could be seen in deep discussions with Kinnear, his former Wimbledon boss, on the pitch before the match.
Kinnear came out to a hostile reception from the Oxford fans at kick-off time, and he responded by making a two-fingered gesture of smoking a cigar, or that's what he seemed to be mimicking.
Playing with wingbacks had perhaps kept United less exposed at the back, yet it was clearly at the expense of committing bodies forward.
But in the second half they seemed to get the balance much better, their midfielders and wingbacks at last supporting the isolated Gray and Scott, and it didn't take long for the nerves to set in among the Luton players.
The home side knew that if they couldn't beat already relegated Oxford, they were as good as down, and the tension among their fans was palpable.
United's first serious attempt on goal came on 50 minutes as John Robertson headed goalwards from 16 yards, with Abbey way out of his goal, but the keeper reached out to save.
Knight then came to United's rescue with the best of his many saves, tipping a Spring header from four yards against the underside of the bar. The ball came down on the line, and must have been very close to being over it, before being half-cleared back to Spring, who then blazed over.
The match changed dramatically on 69 minutes when Beauchamp came on for a disappointing Powell, and the injured Spring had to be replaced by Jude Stirling.
Fear began to assume an even more commanding role, and although Stirling posed a different kind of threat with his long throw-ins, United defended well against them.
Scott's predatory equaliser might have been the prelude to a frantic response from Luton, but that never materialised and, for a change, the U's comfortably rode out the last ten minutes.
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