The food writer Jack Monroe has won £24,000 damages in a libel action against the MailOnline columnist Katie Hopkins following a row over a tweet.
The legal action came after Hopkins implied Monroe had defaced or condoned the damage of a war memorial.
Monroe, 28, told the High Court in London that the tweet had led to death threats and that the subsequent legal dispute had been an "unproductive, devastating nightmare".
The food writer's lawyers said Hopkins' tweet was defamatory and caused "serious harm" to Monroe's reputation, especially as it was a "widely published allegation".
Following the ruling at the High Court awarding her damages, Monroe wrote on Twitter: "It's taken 21 months but today the High Court ruled that Hopkins statements to/about me were defamatory. I sued her for libel. and I won. I'll be writing a longer statement shortly, but for now, to everyone who told me I couldn't, wouldn't, shouldn't – I could, I would, I did."
The legal dispute came after Hopkins, 42, posted a tweet in May 2015 to her 680,000 followers asking if Monroe had "scrawled on any memorials recently".
This followed an incident at an anti-austerity protest when a memorial to the women of the Second World War in Whitehall was vandalised.
The court was told Hopkins had sent the tweet after mistaking Monroe for Laurie Penny, a columnist for the New Statesman, who had tweeted earlier from her account that she "[didn't] have a problem" with vandalism as a form of protest.
Both Monroe – who came to prominence through the blog "A girl called Jack" – and Penny have been outspoken anti-austerity campaigners.
Shortly after Hopkins' tweet, Monroe tweeted in response: "I have NEVER 'scrawled on a memorial'. Brother in the RAF. Dad was a Para in the Falklands. You're a piece of s**t."
A second message read: "Dear @KTHopkins, public apology + £5K to migrant rescue and I won't sue. It'll be cheaper for you and v satisfying for me."
Hopkins deleted her original tweet but lawyers for Monroe said "she did not apologise or retract the allegation even though she knew it was false".
Jonathan Price, for Hopkins, told the judge that "this relatively trivial dispute arose and was resolved on Twitter in a period of several hours".
He argued that "no lasting harm, and certainly no serious harm" had been caused to Monroe's reputation.
But Justice Warby ruled that "whilst the claimant may not have proved that her reputation suffered gravely, I am satisfied that she has established that the publications complained of caused serious harm to her reputation".
He said their publication "not only caused Ms Monroe real and substantial distress, but also harm to her reputation which was serious".
The ruling comes after MailOnline were forced to pay £150,000 to a British Muslim family in December after a column by Hopkins falsely accused them of extremism.