Just five days after regaining the famous urn with a 197-run victory over Australia in the final Test at the Oval, England seemed to be suffering a hangover from their champagne celebrations.
They spluttered to 203-9, with Oval hero Jonathan Trott and Ravi Bopara both dismissed without scoring, and only just managed to hold on as Ireland chased a revised total of 116 in 20 overs after a long rain delay.
Only debutant batsman Joe Denly and Luke Wright impressed after England elected to bat in overcast conditions.
Opener Denly struck 67, while Wrights 36 injected the innings with impetus after England slipped to 135 for six.
An underwhelming start included Trott, whose brilliant hundred on Test debut set up the Oval victory, being trapped lbw by one which nipped back from Australian-raised Trent Johnston.
Bopara, whose wretched time against the Australians led to his omission for the decisive, final Test, also went without scoring to Johnston, after edging a drive to second slip.
Johnstons opening spell of 6-2-7-2 caused the problems for England and was a perfect way for him to celebrate his 100th appearance for his adopted nation.
Matt Prior, captain Paul Collingwood and Owais Shah all perished to skied catches attempting big shots and when Denly was pinned leg before, attempting to swivel the returning Johnston to the leg-side, England were 135 for six.
Twice he cleared the ropes in a rapid 36, which dominated a stand of 42 with Adil Rashid. Only a brilliant catch by John Mooney, flinging himself full length on the run from long-off, halted the 26-ball assault.
Persistent rain stopped the Irish beginning their pursuit for three hours but they finally started with a revised target to aim for. Irelands chase was propelled along by teenager Paul Stirlings positive intent.
Stirling, an 18-year-old on Middlesexs books, hit four fours and a six in an attacking 30 which left them needing marginally over four runs per over for the final dozen overs.
But the hosts seemed to have blown their chance when they subsided from 64-2 to 89-7.
With nine required from the final two deliveries, Johnston lofted to long-on and England 12th man Eoin Morgan, on for Graeme Swann, prevented it clearing the rope by patting the ball back into play.
Johnston and Kyle McCallan, Irelands final pair, ran two but the quick thinking by Morgan prevented a famous victory for his compatriots. Johnston hit the final ball for four but England held on for a narrow victory.