The High Court decides today whether a tweet by Commons Speaker's wife Sally Bercow about Tory peer Lord McAlpine was libellous.
The posting appeared two days after a November 2012 Newsnight report wrongly implicated the former Conservative Party treasurer in allegations of sex abuse at Bryn Estyn children's home in the 1970s and 1980s.
Bercow has always denied that the tweet – "Why is Lord McAlpine trending? *Innocent face*" – was defamatory, but lawyers for the peer said it pointed "the finger of blame" at him during a media frenzy.
Lord McAlpine, who has already received six-figure payouts from the BBC and ITV, said it meant he was a paedophile who was guilty of sexually abusing boys living in care, and wants damages.
Mr Justice Tugendhat, in London, has heard that Mrs Bercow promptly tweeted her apologies, provided letters apologising for the distress caused and making clear that the underlying allegations were untrue, and made an offer to settle the case which had not been withdrawn.
His ruling will determine the actual meaning of the words complained of – both a natural and ordinary meaning and an innuendo meaning.
If the judgment goes in Lord McAlpine's favour, there will be another hearing at a later date on the appropriate level of damages, unless the two sides reach a settlement.