Harrison improved his record to 27 wins and four defeats
Audley Harrison produced a stunning last-round left hook to stop Michael Sprott and perhaps keep his faint world title hopes alive.
Harrison went into the fight claiming he was close to challenging for a world heavyweight title, but by the final round was behind on all three cards.
Despite an injured right shoulder, he caught Sprott with a huge shot to secure the vacant European title.
"I showed a lot of heart. Losing wasn't an option," Harrison told Sky Sports.
For most of the fight Harrison looked set for a defeat that would - by his own admittance - have put his career in doubt.
He took the first, landing with a series of jabs to keep Sprott at distance, but he was rocked by a right hand in the second and only awakened from his slumber six rounds later.
During that period, he might have edged a forgettable third, but made Sprott look far more dangerous than a record of 17 stoppages in 46 fights and only two in the past five years might suggest.
Still, one of those stoppages was of course against Harrison in February 2007.
You've got to give credit to Harrison, he found it from somewhere
Harrison was warned for resting his right, rather than throwing it as a jab in the fourth and a switch to orthodox in the fifth suggested a problem, later confirmed as a damaged shoulder.
Sprott continued to dominate the centre of the ring and even a switch back to southpaw did little to immediately change the momentum, Harrison laboriously pushing out the occasional right-handed jab to break lengthy periods of inactivity.
Harrison had won five of his last six fights going into the contest and proved his stamina by winning three contests in the same evening to win the Prizefighter crown.
And a one-armed barrage in the eighth suggested he could still turn the tide, but Sprott went back on the offensive in the 10th and when he also edged the 11th the fight appeared to be up for Harrison.
His one chance was a stoppage, but it was Sprott who initially looked more likely to end the contest prematurely as he surprised Harrison with a barrage of his own.
However, showing a desire that has not always been immediately evident, Harrison weathered the blows, turned Sprott and landed with a perfectly timed left to end the contest.
Having come within seconds of a defeat that would have made a mockery of pre-fight assertions that he could face one of the Klitschko brothers for a world title, Harrison said: "I had to win it somehow.
"Michael was courageous, but I think I showed a lot of fight. That shows I wanted to be European champion and keep my career.
"He came in with a game plan, but with one shot I showed a lot of bottle and that I deserve to be champion."
After receiving treatment in the ring, Sprott said: "You've got to give credit to Harrison, he found it from somewhere.
"I was ahead, but that's heavyweight boxing - one shot and it's all over."
On the same bill, Barnet's Darren Barker beat Affif Belghecham by unanimous decision to extend his perfect record to 25 fights and win the vacant European middleweight title.
Barker dominated the first part of a keenly-contested match-up before Belghecham rallied in the second half to close the gap.
The judges scored the fight 116-114, 116-112 and a lopsided 116-110.