A knock on the door. A gift of diamonds. Nothing unusual, says Campbell

The supermodel's evidence against Charles Taylor could prove crucial. Mark Hughes reports from The Hague

Her testimony could prove crucial in prosecuting one of the world's most fearsome dictators and securing justice for thousands of victims of a brutal civil war. For Naomi Campbell, though, it was all a terrible inconvenience.

The famously truculent supermodel was typically and fashionably late, and when she did arrive she made it clear she would rather be anywhere else than a courtroom in The Hague, declaring: "This is a big inconvenience for me."

But the information Naomi Campbell imparted could ultimately help establish the all-important link between the former Liberian president Charles Taylor and the blood diamonds he is alleged to have traded in.

Since 2007, when the trial opened, the prosecution has tried desperately to prove that Mr Taylor, in exchange for diamonds, facilitated atrocities in Sierra Leone by providing arms to rebel groups who would go on to murder more than 100,000 civilians.

But, with the exception of one former member of Mr Taylor's staff who claimed he saw jars stuffed with stones, there has been little evidence from any of the 91 witnesses that puts Mr Taylor in possession of blood diamonds.

Yesterday the 92nd witness – a model from south London – provided testimony which may help do just that.

Dressed in a figure-hugging cream dress and with her hair in a bun, the 40-year-old told, in her soft London-meets-Manhattan accent, the story of how, after meeting Mr Taylor at a 1997 party at Nelson Mandela's presidential residence in South Africa, she was awoken by a knock at her bedroom door in the middle of the night.

Answering the door, half-asleep and wearing a nightdress and a cashmere shawl, Ms Campbell was met by two men whom she believed to be part of Mr Taylor's entourage and given a pouch containing unfinished diamonds.

Without deigning to ask the identity of the men, she simply closed the door and returned to bed because she was "exhausted" after traversing three continents in three days.

The story provoked gasps of amazement from the 84 media members and diplomats in the public gallery above the courtroom – not least because Ms Campbell has previously publicly denied receiving diamonds on that evening.

But apparently it was an event not out of the ordinary in the world of Ms Campbell. "It is not abnormal for me to get gifts," she told the court. "I get gifts all the time: sometimes in the middle of the night without knowing who they are from. It is quite normal for me."

While she said she could not be sure that the men were working for Mr Taylor, she "assumed they were".

She made a similar assumption as to the identity of the stones. After discussion with her former agent, Carole White, and the actress Mia Farrow, over breakfast the following morning she accepted they were likely to be diamonds, But originally she said she thought they were "dirty-looking pebbles".

"When I am used to seeing diamonds I am used to seeing them shiny and in a box. If someone had not said they were diamonds I would not have guessed."

The recollection could have telling repercussions for Mr Taylor, but if he was worried he did not show it. He carefully followed proceedings, changing his spectacles at times, and jotting down notes in a large pad.

But while her testimony was compelling and possibly crucial, Ms Campbell did not seem to care. She did not want to give evidence and made no bones about saying so. "I do not really want to be here. I was made to be here. I want to get this over with and get on with my life."

Ms Campbell was forced to testify because of statements made to the court by Ms White and Ms Farrow. Both women said they recall Ms Campbell talking about being given the diamonds.

Ms Campbell rejected requests to appear at court and eventually had to be subpoenaed to appear, at the threat of being jailed. Her late arrival caused a delay which prompted mention from the judge, Justice Julia Sebutinde, who said: "Where is she?" Later, when asked about her timekeeping, Ms Campbell replied with a smile: "I'm always late."

After taking her seat inside Special Tribunal Room Two – a former basketball court which now resembles a padded cell – Ms Campbell swore on the bible to tell the truth. Asked her profession she replied: "I am a model and self-employed business woman and I do a lot of charity work."

She said she was not nervous, but throughout her evidence she fiddled with a small lace purse in her hands.

When asked about the evening in September 1997 she carefully listed the other guests at the dinner party, who included Nelson Mandela, Quincy Jones and Imran and Jemima Khan, but missed the most crucial name.

"There were some other people, I do not recall. It was 13 years ago," she said. After some prompting, she remembered that Mr Taylor was at the meal and went on to recount the story of being given the diamonds in the night.

Being unwilling to testify is not unusual. But in Ms Campbell's case it cannot be because of unfamiliarity with a courtroom. She has appeared in court on repeated charges of assault and, on one occasion, to challenge a newspaper article which accused her of taking drugs. Those appearances have been noted for their farcical nature. Yesterday's was no exception.

At one point, while attempting to explain that she did not know Mr Taylor before dining with him, Ms Campbell said she had never heard of Liberia.

"I had never heard of him before. I had never heard of Liberia before. I had never heard the term blood diamonds." She later denied she had swapped phone numbers or flirted with Mr Taylor. Asked if she had spoken to him during the dinner, she replied: "Not pacifically[sic], no. When I am in Mr Mandela's presence, Mr Mandela is my focus."

The previous 91 witnesses, many missing limbs, have testified to the brutality of the rebels allegedly armed by Mr Taylor to a near empty court. More than 200 journalists attended yesterday's hearing. A tiny fraction of that has attended previous hearings.

It was a point illustrated perfectly by the empty gallery accompanying the testimony of Issa Sesay, an alleged rebel leader and the next witness.

In her final piece of testimony Ms Campbell said she had given the diamonds the next day to Jeremy Ratcliffe, the head of the Nelson Mandela Children's Fund (NMCF), and asked him to "do something good with them".

She said she had since spoken to Mr Ratcliffe last year and that he said he still had the diamonds. But the court was shown a letter which showed the NMCF – to which Ms Campbell donates $50,000 a year – had no record of receiving a diamond gift and that it would be illegal to do so.

But that was clearly not troubling Ms Campbell, who said: "Once I had given them over it was out of my hands and I did not really care about it any more. I did not really care what he did with them as long as he did something good."

As she left Ms Campbell was given a sardonic parting: "We want to thank you for your testimony," said Mrs Justice Sebutinde. "And for taking time out of your busy schedule."

In her own words...

Naomi Campbell on diamonds...

"They [the ones she was given] were dirty-looking pebbles. When I am used to seeing diamonds I am used to seeing them shiny and in a box."

... African geography

"I had actually never heard of Liberia."

... Being a witness

"This is a big inconvenience for me. I don't really want to be here. I was made to be here. I want to get this over with and get on with my life."

... Charles Taylor

"This is someone, I read on the internet, killed thousands of people, supposedly, and I don't want my family in danger."

... Receiving gifts

"It is not abnormal for me to get gifts. I get gifts all the time: sometimes in the middle of the night without knowing who they are from. It is quite normal for me to receive gifts."

... Timekeeping

"I am always late."

... Her personality

"I am someone who lives my life but I am not about showing what I have."

Explainer: Why the case is being heard

Q. Who is Charles Taylor?

A Liberian lay preacher, rebel leader, politician and former president, Charles Taylor was central to the conflict in the West African nation. He was born into the Americo-Liberian elite in the country founded in the 19th century by the US with freed slaves. He started his career in the 1980s under thuggish coup leader Samuel Doe, a man he later overthrew with American help. He won an election in 1997 to confirm his presidency but was eventually persuaded to stand down and move into exile in Nigeria.

Q. Why is he on trial at the International Criminal Court?

The former Liberian president faces with 11 counts of war crimes, crimes against humanity, and other serious violations of international law committed during the Sierra Leone conflict that ended in 2002. The prosecution is seeking to prove that he was a major backer of the RUF rebel group in neighbouring Sierra Leone and sponsored a second warring faction, as well as Liberian forces supporting these rebels. They are also trying to prove that these military actions were funded by the sale of so-called blood diamonds.

Q. What happened during the Sierra Leone conflict?

The struggle, fought largely for control of natural resources such as diamonds and timber, was among the worst of Africa's wars. Much of it was fought by child soldiers. The war was marked by brutal attacks against civilians, including murder, rape, abduction and mutilation. Taylor's forces, including the notorious "Small Boys Unit", were also involved in horrendous crimes against humanity inside Liberia during his struggle for power with his predecessor, Samuel Doe.

Q. How was he arrested?

Taylor was indicted by the special tribunal from the ICC in 2003. Soon afterwards, he left Liberia to take sanctuary in Nigeria after rebel forces threatened to overrun the capital, Monrovia. Initially, he was protected by the Nigerian government, but after the election of Ellen Johnson Sirleaf in 2006 that protection was withdrawn. Taylor attempted to escape with large amounts of cash over the border into Cameroon but was apprehended. He then made a brief appearance at the Freetown Tribunal under heavy UN guard before being transferred to The Hague.