Northampton have been waiting for this since October. Five months ago their unbeaten start to the Aviva Premiership ground dramatically to a halt in Reading when London Irish registered a bonus-point win on their own turf; here they returned the compliment with interest – or "icing" as Brian Smith, Irish's director of rugby, said.
Utterly dominant in the set-piece, Northampton's six-try success carried them into the play-off places for which they yearn. They have had their problems in the middle part of this season but, buoyed by the presence of Dylan Hartley, their captain returned from England duty, they played the muscular rugby which has become their trademark.
The line-out statistics were the most revealing: it is a phase of play where Irish have traditionally been market leaders but here they were outmanoeuvred by 21-5, losing four of their own throws in an appalling turnover rate of 23 in all phases of play. Stephen Myler could play ball in hand or territory, a balance which clearly appealed to Jim Mallinder, Northampton's director of rugby.
"The forwards were good but we also made good decisions behind the scrum," Mallinder said. "We scored tries from our set-piece and maul but also out wide. Our two England lads [Hartley and Courtney Lawes] were particularly impressive, they put their bodies on the line. I hope Stuart Lancaster [the England head coach] will watch the game because it will give him some selection headaches."
Northampton, of course, have another "England lad" in Ben Foden, whose serious ankle injury cost him his place in the autumn internationals. On this evidence he is rediscovering his potency slowly.
Hartley was named man of the match on a sunlit afternoon when Jamie Elliott, the 20-year-old product of Northampton's academy, scored three tries and denied the Irish one with his intelligent covering.
The result would have been no different had the Irish made the most of their opportunities in the first quarter; on another day there might have been two tries rather than the three penalties kicked by Tom Homer but, unable to control the ball, they would still have suffered.
Smith was able to give Setaimata Sa, his Samoan dual-international, his first appearance off the bench and expects to build a back division around the centre over the next three years. "He's a lovely ball player, a big strong fellow, he can offload effectively, distribute and carry the ball, he's the real deal," said Smith, who also paid Northampton the compliment of being the kind of genuine club to which Sa needs to be exposed as he makes his way in the Premiership.
The Irish have flirted with relegation for much of this season but, with Sale Sharks well beaten and London Welsh facing a disciplinary hearing on Tuesday which is expected to cost them league points, that threat may have eased. This, though, was an abrupt reminder that no chickens can be counted by those near the bottom of the table.
Northampton B Foden; J Wilson, G Pisi, T May (D Waldouck, 55), J Elliott; S Myler (R Lamb, 63), L Dickson (M Roberts, 63); S Tonga'uiha (A Waller, 58), D Hartley (capt; R McMillan, 68), T Mercey (B Mujati, 51), C Lawes, C Day, S Manoa (M Sorenson, 58), G J van Velze, P Dowson (B Nutley 27-34, 51).
London Irish T Homer; T Ojo, G Armitage, S Geraghty (S Sa, 71), M Yarde; I Humphreys, P Phibbs (J Moates, 58); M Lahiff (J Yanuyanutawa, 74), S Lawson (D Paice, 51), H Aulika (L Halavatau, 71), G Skivington (K Low, 74), B Evans (captain), M Garvey (J Sinclair, 51), J Fisher (J Gibson, 71), O Treviranus.
Referee J P Doyle (London).
Tries: Elliott 3, Manoa, Tonga'uiha, Van Velze
Cons: Myler 4, Lamb
Pens: Homer 3