By legal affairs correspondent Jane Peel

When Neil Hamilton decided to sue Mohamed al-Fayed for libel he knew his opponent would face a huge burden.

To defend himself, Mr al-Fayed would have to come up with strong evidence to prove the former MP had taken his money and hospitality as a corrupt payment for parliamentary services.

It must have seemed like a sure bet for Mr Hamilton. Even if something is true, it is not always easy to prove it. Mr al-Fayed had no documentary evidence to show that Mr Hamilton had taken bundles of cash, and substantial Harrods gift vouchers. He could prove Mr Hamilton and his wife, Christine, had enjoyed a lavish six-day stay at the Ritz Hotel in Paris at the expense of Mr al-Fayed - but could he prove that the hospitality was corrupt?

Mr Hamilton might also have gambled that Mr al-Fayed - an extremely wealthy businessman - would offer to settle the case before the trial began, unwilling to put himself through the ordeal of cross-examination on his unorthodox and often shocking opinions and his controversial background.

Someone's lying, but who?

That first gamble didn't pay off. Even persuading the court to take the unusual step of hearing the defence case first did not help. This had the effect of forcing Mr al-Fayed to go into the witness box before Mr Hamilton and justify his claims.

So in the end it was a question of how strong the evidence called by each party was and which of the two protagonists the 11 jurors disliked most or liked least.

One of them was lying - they had to decide who that was.

Mr Hamilton's lawyers sought to discredit Mr al-Fayed as an habitual liar, a vindictive employer and totally untrustworthy.

Surely if they could succeed, then no jury could believe anything he said - particularly if he had no hard evidence on the "cash for questions" allegation?

'Corrupt' payments from Mobil

So why did the six women and five men of the jury decide Mr Hamilton was indeed corrupt and had taken the money?

The law prevents us from asking jurors why and how they reached a decision, but there seems little doubt that they would have paid great attention to one part of the evidence that emerged at the 11th hour.

During legal argument, Mr al-Fayed's formidable QC, George Carman, persuaded the judge to allow in evidence the fact that Mr Hamilton had in 1989 received a payment of £10,000 from the multi-national oil company, Mobil.

Mr Carman said this was irresistible evidence of corruption - Mr Hamilton had demanded the money as payment for tabling an amendment to a Finance Bill on behalf of Mobil.

Mr Hamilton tried to persuade the jury the money was a legitimate consultancy fee and nothing to do with the amendment he put forward (which would have saved Mobil millions of pounds in tax).

But he was contradicted in court by three witnesses - two Mobil executives (one now retired), and a leading tax barrister, Peter Whiteman QC who is an adviser to Mobil and who introduced Mr Hamilton to the company.

Shocking demands for cash

All three witnesses told the court there was no consultancy agreement in place when Mr Hamilton asked about payment terms.

Two of them said they were shocked when Mr Hamilton demanded money. Mobil eventually paid him because the executives felt they had a "moral obligation" to do so after he'd helped them out.

They then set up a consultancy agreement as an "expedient" way of explaining the payment.

Although there were inconsistencies in the evidence of the three witnesses, all of them agreed with the thrust of the defence case - that there was no legitimate consultancy in place when money was demanded.

Consultancy a sham

It was devastating to Mr Hamilton's argument. Three people - two of them totally unconnected with Mr al-Fayed (Mr Whiteman was Mr al-Fayed's tax adviser too) were, in effect, supporting the suggestion that Mr Hamilton was corrupt.

If the "consultancy agreement" was a sham, then corruption was proved. It wasn't the corruption Mr al-Fayed alleged and which was the subject of the libel action, but if Mr Hamilton was corrupt over Mobil, then it went some way to proving he had acted corruptly over cash for questions.

The jurors clearly took the Mobil matter seriously. During their eight and a half hours of deliberation, they sent a question to the judge, asking him to repeat some of Neil Hamilton's evidence on the subject.

Journalists who covered the five week trial are convinced the Mobil issue was a turning point.