It was about as clean and precise as a bout of mud wrestling, but Harlequins had enough class in crucial areas to inflict on Northampton their fourth defeat in five home matches. A tactically absorbing battle might have taken a different course if Saints had been allowed a second-half "try" by Ben Foden that was pulled back for a forward pass in the build-up.
Not for the first time this season there was a row over video replays – the lack of use of one, rather than any disagreement over what it showed – as Jim Mallinder, the Northampton director of rugby, described referee Wayne Barnes's decision to halt play on the advice of his assistant as "ridiculous". Others might say Barnes was quite right to call what he saw rather than wait to hit the rewind button.
"Why have the technology like that and not use it?" asked Mallinder, referring to the trial regulation that allows the run-up to a try to be reviewed as long as play has not stopped. Foden had caught George Pisi's flipped pass in the 22nd minute and weaved to the line only to see Barnes, stationed 30 metres back down the field, indicating there had been a forward pass in what was an extremely tight call.
So instead of a five- or seven-point lead for Saints, the scoreline stayed at 3-3, and it had moved on only to 6-3 to Quins by the 55th minute, at which time the visitors' impressive tighthead prop James Johnston went to the sin-bin for a blatant flop on the wrong side of a ruck. Those of a multi-coloured persuasion might have recalled a win here on New Year's Day 2011, when they were down to 13 men for a while.
There must have been similarly deep satisfaction among the reigning champions that they gradually pulled clear this time. Though initially pegged back to 6-6 by Steve Myler's second penalty on 57 minutes, Harlequins rallied to lead by six points while still down to 14 men.
All the Quins' scores came from the fly-half Nick Evans's boot: the All Black had two penalties in the first half and two more in the final 10 minutes, either side of one by Myler's replacement Ryan Lamb. But Evans for once was a comparatively peripheral figure. For every piece of possession spilled in contact – and they must have been in double figures – there was a committed tackler, and Quins, led by Chris Robshaw, had plenty of those.
They also had Mike Brown enjoying himself at full-back – not the wing position he occupied for England during the autumn, when Saracens' Alex Goode had the No 15 jersey – with raking positional kicks and one outstanding defensive catch of a Myler cross-kick that launched a rousing 70-metre run-and-hack gallop by Nick Easter via Robshaw's smart inside pass.
Mallinder's counterpart, Conor O'Shea, praised the "top-notch performance levels" throughout his team and said he had met England coaches Stuart Lancaster and Andy Farrell together with Brown a week ago to discuss the full-back – or is he a wing? "Mike wants to play at full-back for England," said O'Shea, "though he will play anywhere to be in the team. My selection would be different."
So Harlequins will spend a happy Christmas positioned at the top of the Premiership and expecting Boxing Day to see them sell the last of the 81,600 tickets for Saturday's Big Game against London Irish at Twickenham. The mood at Northampton is difficult to judge. Near silence greeted the final whistle, as the home support digested the continuing run on this ground of losses since October to Saracens in the league, Harlequins in the LV Cup and now the league, and Ulster in the Heineken Cup, much as they cheered last week's win in Belfast that kept Saints alive in Europe. "We have won three out of our last five so we're getting something right," said Mallinder. "We won't lie down, we'll go to Saracens next week and show the reaction we did last week. We have just come up against two of the best sides in Europe." Doubtless there are Saints devotees who would like to think of their own team in that bracket but this loss pushed Northampton out of the Premiership's top four, in the absence of their suspended captain Dylan Hartley, even if they were tipped by O'Shea to recover and reach the play-offs. There were a lot of mauls – if it hadn't been for the use-it-or-lose-it law, the ball might have been out of sight all afternoon – and lost line-outs, for which disruptive defence should take some credit.
Northampton kicked two penalties to touch in the first half rather than take long pots at goal but secured no points. Another regret to be lingered over was the extension of Quins' Indian sign over them to one loss in six meetings.
Northampton Saints B Foden; K Pisi, G Pisi, T May (D Waldouck, 57), J Elliott; S Myler (R Lamb, 72), L Dickson (M Roberts, 72); S Tonga'uiha (A Waller, 63), M Haywood, P Doran Jones (B Mujati, 52), S Manoa, C Lawes (M Sorenson, 69), P Dowson (capt), GJ van Velze, T Wood.
Harlequins M Brown; T Williams, M Hopper, T Casson, U Monye; N Evans, D Care; J Marler (M Lambert, 67), J Gray, J Johnston, O Kohn, G Robson, M Fa'asavalu (W Collier, 60-67; T Guest, 67), N Easter, C Robshaw (capt).
Referee W Barnes (London).
Pens: Myler 2, Lamb
Pens: Evans 6