His victory came after one of the most bitter and vituperative run-ups to the prize in living memory - not among the shortlisted writers, but from dismayed and bemused commentators who accused judges of putting populism above genuine quality.
But few of those critics could claim Barnes' novel is not of the highest quality. The chair of this year's judges, former MI5 director general Stella Rimington, said it had "the markings of a classic of English Literature. It is exquisitely written, subtly plotted and reveals new depths with each reading."
Much of the row over the shortlist has stemmed from Rimington's own prioritisation of "readability" in the judging criteria. But tonight, she said quality had always been just as important.
"It is a very readable book, if I may use that word, but readable not only once but twice and even three times," she said. "It is incredibly concentrated. Crammed into this short space is a great deal of information which you don't get out of a first read."
The book, at 150 pages, is undoubtedly short, but not the shortest to ever win the prize – that record belongs to Penelope Fitzgerald's Offshore, which won in 1979 and is shorter by a few hundred words.
The Sense of an Ending, Barnes' 11th novel, explores memory: how fuzzy it can be and how we amend the past to suit our own wellbeing. It tells the story through the apparently insignificant and dull life of arts administrator Tony Webster.
"One of the things that the book does is talk about the human kind," said Rimington. "None of us really knows who we are. We present ourselves in all sorts of ways, but maybe the ways we present ourselves are not how we really are."
Rimington said the question of whether Barnes was overdue to win the £50,000 prize never entered her mind or figured in the debate. "We really were, and I know you find it very boring of me to say so, looking at the books that we had in front of us," she said.
Despite the sometimes hostile reaction to the shortlist, Rimington said she had enjoyed the process of judging. "I've been through many crises at one time or another in which this one pales, I must say. We've been very interested by the discussion. We've followed it sometimes with great glee and amusement. The fact that it has been in the headlines is very gratifying."
It took the judges (Rimington, MP Chris Mullin, author Susan Hill, the Daily Telegraph's head of books Gaby Wood and he Spectator editor Matthew d'Ancona) just 31 minutes to decide on the winner, after what Rimington called "an interesting debate." They had been divided 3-2 at the beginning of the judging meeting, but were all agreed by the end.
"There was no blood on the carpet, nobody went off in a huff and we all ended up firm friends and happy with the result," she said.
Barnes, 65, had been shortlisted for the prize three times previously; in 1984 with Flaubert's Parrot, when he lost out to Anita Brookner; win 1998 with England, England, losing to Ian McEwan; and with Arthur & George in 2005, when he lost to John Banville.
What was particularly striking this year was that Barnes was the only seriously big hitter on the shortlist, and the only author to have been shortlisted previously.
Much more at The Guardian.