In his closing speech, George Carman QC, for Channel 4, told the six men and six women who have listened to 10 days of evidence: 'You, and you alone, will decide which witnesses deserve from you a seal of approval for truthfulness . . . You will decide where sits the enemy of truth in this courtroom.'
Miss Allan, 40, a South African journalist who now lives at Hampton Court, south-west London, is suing for damages over the film The Leader, His Driver and the Driver's Wife, which she claims falsely portrayed her as a 'lady of easy virtue' who had an affair with Eugene Terre-Blanche, the leader of the AWB, the South African far-right party.
Channel 4 said the programme did not suggest an affair, but even if it had the allegation would be justified. During the trial, Mr Justice Potts and the jury have heard defence witness Linda Shaw, Miss Allan's former flatmate, say she looked through a keyhole and saw Miss Allan and Mr Terre-Blanche having sex.
Mr Carman asked the jury: 'Is this woman, Miss Allan . . . an innocent woman, as she would claim, unjustly wronged by a TV programme?' It was Channel 4's submission that Miss Allan's case was 'so seriously flawed in so many respects' that on analysis it was 'really unworthy of belief'.
The documents and tape recordings produced to support the defence case cast 'a flood of light' on where the truth really lay. 'They really portray Miss Allan as having been, sadly, gravely untruthful in the witness box,' Mr Carman said.
The jury should consider the 'compelling weight' of evidence from six defence witnesses, five of whom had spoken out in front of them. 'The case may have proved an entertainment for others, but not for the witnesses involved - and above all, not for Miss Linda Shaw.'
In his closing speech for Miss Allan, Charles Gray QC said: 'On the one hand we have Jani Allan saying adamantly and repeatedly to you that she never had any kind of sexual relationship with Terre-Blanche. On the other hand we have a band, a planeload, of witnesses from South Africa, each of whom when they came into the witness box grabbed every opportunity to assert or imply sex had taken place between Terre- Blanche and Jani Allan.'
He reminded the jury they did not decide these things by adding up the witnesses on each side. He asked whether they really believed that if, as Channel 4 asserted, Jani Allan had had a passionate fling with Mr Terre-Blanche, she would have had the 'gall' to start the action 'founded upon a lie'.
Mr Gray said Channel 4 had to prove Miss Allan had sexual intercourse with Mr Terre-Blanche. Her sexual conduct, which would normally be a private matter, had become an issue for public debate because Channel 4 chose to drag her into the film 'quite unnecessarily and quite gratuitously'.
Of Miss Shaw's 'keyhole' evidence, Mr Gray said: 'I don't know what the female equivalent of a Peeping Tom is, but it must be a fair description of Miss Shaw.'
Miss Shaw's evidence was 'wildly unlikely'. She could never have seen through the keyhole what she said she had seen. Her field of vision was not big enough.
Mr Gray said the jury should award Miss Allan a substantial sum in damages. It should reflect the damage to her reputation; her indignation and upset; her anxiety awaiting the trial; her embarrassment; the harrowing ordeal she had undergone in court; and the physical effect of the case.
The hearing was adjourned until today when the judge will sum up. The jury is expected to retire to consider a verdict tomorrow.