The last unbeaten record in the Aviva Premiership was ground into the dust yesterday. Northampton may have retained their top spot thanks to the demise of Harlequins in the West Country, but they will have left feeling nothing like leaders.
Not even the most hardened London Irish enthusiast would have seen this coming: the team that started the day second from bottom, with one win from five outings, played such convincing rugby that they posted a reminder of that blissful 2008 season when they made their way to the last four in Europe.
They took on the Northampton set-piece and came out ahead, they rolled their mauls so many metres that Northampton will blush to remember and their two half-backs ran the most effective of shows. Tomas O'Leary was a constant thorn, and Ian Humphreys will be hard to dislodge from fly- half so composed was he.
More to the point, they played the attacking rugby on which Brian Smith, their director of rugby, is insistent. Yet they allied offence to a far more aggressive defence, the area which let them down last month. "Northampton came with a monster pack. It was a big challenge because confidence has not been high," Smith said. Hence the selection of Jamie Gibson, 22, at openside flanker, and how well he responded. Northampton fielded three England caps in their back row but the tall blond youngster played the most thoughtful of games, as well as scoring the try that gave Irish their first try bonus point of the season.
Most of Gibson's senior rugby has been on the blindside, where Courtney Lawes continued his comeback on an afternoon which Jim Mallinder, Saints' director of rugby, described as "an embarrassment". "Mentally I don't think we were up for the game," Mallinder added, refusing to accept the late withdrawal of James Wilson, with a pulled muscle, as an excuse.
That left Vasily Artemyev filling in at full-back, where the Russian wing was clearly not at home. His uncertainty spread to his colleagues; not one of Northampton's traditional strengths served them well in the absence of injured captain Dylan Hartley, who should be back from an eye injury for next weekend's European campaign.
Perhaps Northampton knew it would not be their day when the first scrum of the match earned them two free-kicks and then a penalty to their opponents. That was followed by an overthrown Northampton line-out which fell for Ofisa Treviranus. The ball was kicked through by Jonathan Joseph and Marland Yarde, with Joseph getting the touchdown.
The goalkicking of Steven Shingler was not at its best but the full-back added a penalty and converted a try by David Paice, the hooker shunting his way over after the initial break by O'Leary.
When Humphreys knocked over a 40-metre drop goal Northampton, who have been scoring first-half points for fun, trailed 18-0 at the interval; midway through the second half, the difference was 30.
Joseph's break and accurate pass gave Topsy Ojo the chance to finish strongly through the tackles of Luther Burrell and Ken Pisi. Another perceptive pass, this time by Shingler, found Treviranus lurking on the wing and he gave Gibson a 40-metre gallop to the line.
By this time Northampton were playing only for pride. Pisi, the best of their backs, recovered one try as a raft of changes allowed the Irish to restore an Armitage (Guy, the younger of the brothers who decamped to Toulon in the summer) to their ranks.
Shingler kept knocking over penalties and Dowson's close-range try for Northampton did nothing to make the journey home any more comfortable.
London Irish S Shingler; T Ojo, J Joseph, S Tagicakibau (G Armitage, 66), M Yarde; I Humphreys (S Geraghty, 66), T O'Leary (J Moates, 62); M Lahiff, D Paice (S Malton, 75), H Aulika (A Cotter, 59), G Skivington (K Low, 76), B Evans (capt), M Garvey, O Treviranus (C Hala'ufia, 62), J Gibson.
Northampton V Artemyev (R Lamb, 50); K Pisi, D Waldouck, L Burrell (T May, 62), N Cato; S Myler, L Dickson (M Roberts, 65); S Tonga'uiha (A Waller, 62), M Haywood R McMillan, 62), B Mujati (P Doran-Jones, 59), S Manoa (R Oakley, 62), M Sorenson, C Lawes, P Dowson (captain), T Wood (T Harrison, 70).
Referee M Raynal (France).
Tries: Joseph, Paice, Ojo, Gibson
Cons: Shingler 2
Pens: Shingler 4
Drop goal: Humphreys
Tries: Pisi, Dowson
Cons: Myler 2