Ulster arrived hoping to confirm themselves as Europe's coming force. Instead they sank to the bottom of Heineken Cup Pool Five, vanquished by a fly-half, Shane Geraghty, of Irish extraction but with designs on playing for England.
Geraghty, 20, is on England's sevens roster, and though his father is from County Mayo his salad days are set to be on the exiles' side of the water. His try just after the hour was the beginning of the end for Ulster, whose own much-longer-in-the-tooth No 10, David Humph-reys, was fatally flummoxed by the home side's rush defence.
This was the first meeting in a competitive fixture between Irish and any of the four provinces, and on such an occasion the "Irishness" or otherwise of the club comes into focus. Only six of the 38-man senior squad are Ireland-qualified, and one of those is Geraghty. Although the club are Irish-owned and the giddying swirl of music, Guinness and craic at the Madejski Stadium is an unmistakeable brand statement, for this win which maintains their say in Europe they relied on recruits from all corners of the planet.
Ulster scored first with a 40-metre penalty by Humphreys, but Irish scored tries in the 17th and 20th minutes. First a lovely slipped pass by the Samoan centre Seilala Mapusua sent the Argentinian No 8 Juan Leguizamon over. Then England's Mike Catt showed all his instinctive wiles with a half-volley towards the posts and the bounce he wanted on the end of it to make the most of a chip by Geraghty, who converted both tries.
Humphreys kicked a second penalty after 33 minutes, when Geraghty was caught not releasing by Kieron Dawson, a London Irishman for 10 years before he joined Ulster last season. It had needed something decisive from a Dawson or a Neil Best - the wild-haired flanker described by Keith Wood during a recent Ireland match as "just mad, really"- to get Ulster into the match, and they finished the first half in their pomp. A rattled Irish lost two men to the sin-bin - Delon Armitage for a neck-high tackle on Bryn Cunningham and Justin Bishop for tripping Isaac Boss - and with Ulster's backs temporarily in the groove, Paul Steinmetz got outside Mapusua for a try, converted by Humphreys.
Still Irish led 14-13, and they survived being two men light at the outset of the second half with not a point conceded, due to Humphreys missing a penalty from middling distance and Ulster's inability to fashion any sustained handling. Irish were restored to their full number, and they had Ulster's number; a spectacular break led by Catt, Mapusua and the galloping Leguizamon took them deep into their opponents' 22. After a couple of scrums the simplest of dummies by Geraghty took him through Humphreys and Paddy Wallace to the posts. Many of Ulster's supporters were clad in Santa costumes, but this was a gift too far. Geraghty converted and Irish led by eight, with a bonus point beckoning if they could score a fourth try.
They appeared keener on shutting up shop, with Geraghty and Catt substituted. A penalty and backchat by Ulster's Australian lock Justin Harrison brought Geraghty's replacement, Barry Everitt, into goal-kicking range and he made it 24-13. But there was just time to give the ball some more air, and sleight of hand by the irrepressible Leguizamon guided another Samoan, Sailosi Tagicakibau, into the left corner. It was Ulster's ninth European Cup match in England, and their ninth defeat.
London Irish: D Armitage; J Bishop, S Mapusua, M Catt (capt; G Tiesi, 74), S Tagicakibau; S Geraghty (B Everitt, 74), P Hodgson; N Hatley (M Collins, 48), R Russell (D Coetzee, 48), T Lea'aetoa (F Rautenbach, 61), N Kennedy (J Hudson, 77), B Casey, K Roche (P Murphy, 55), J Leguizamon, S Armitage.
Ulster: B Cunningham (M Bartholomeusz, 64); T Bowe, P Steinmetz, P Wallace, A Trimble; D Humphreys, I Boss; B Young (J Fitzpatrick, 61), R Best, S Best (capt), J Harrison, M McCullough (T Barker, 46-56), N Best, R Wilson, K Dawson (N McMillan, 74).
Referee: J Jutge (France).