Media playback is unsupported on your device Media caption James Thomson was there when Charles Ingram 'won' the Millionaire jackpot

A former contestant on the TV quiz show Who Wants To Be A Millionaire says he may have inadvertently helped Charles Ingram cheat his way to the jackpot.

James Thomson, 64, was in the studio audience on the night in 2001 when the money was won.

He says he innocently gave an answer to Tecwen Whittock, who was later convicted of his part in a plot to use coughing to signify correct answers.

"I happened to know the answer," said Mr Thomson. "The rest is history."

The prosecution case against Ingram and Whittock, as shown this week in a three-part ITV drama about the incident, was that when Ingram did not know the answer to a question, he verbally listed the four options. At that stage, Whittock - who was another contestant on the show, sitting in the "fastest finger first" seats - coughed to signify which one Ingram should choose as his final answer.

But as the drama, called Quiz, showed, Whittock was himself stumped when it came to the £1m question, which was "A number one followed by one hundred zeros is known by what name?".

At that stage, the drama showed, he whispered to a fellow contestant in the "fastest finger first" seats to ask his opinion - but Mr Thomson, who was sitting in the studio audience close to Whittock, says that he also quietly conferred with him.

Because their conversation was seemingly out of earshot of Ingram and the show's host Chris Tarrant and there seemed to be no harm in discussing it, Mr Thomson told Whittock that he knew the answer was "Googol".

Background noise

Ingram, a former British Army major, and his wife Diana, both 39, and college lecturer Whittock were all found guilty in 2003 of conspiring to cheat the show.

Image copyright Getty Images Image caption Charles and Diana Ingram received suspended jail sentences

The court found that Ingram, who reached the £1m prize, was guided to correct answers with the help of deliberately timed coughs from Whittock.

James Thomson, a retired retail manager who was originally from Belfast but now lives near Lincoln, admits he did not realise that the coughing on the night was deliberate, but says he was suspicious about how the top prize was won.

He told BBC News: "I have to say that I wasn't aware of any coughing.

"I was concentrating more on Major Ingram and Chris Tarrant all throughout the programme.

"I wasn't really aware of any background noise. People cough and sneeze and everything else, but when it got to the million pound question, strangely I happened to know the answer."

Image copyright ITV Image caption Sian Clifford and Matthew Macfadyen play Diana and Charles Ingram in a three-part ITV series entitled Quiz.

He said it was clear that Charles Ingram "clearly hadn't the foggiest idea of what the answer was".

"He said 'I think it's googol' and at some point in that exchange Tecwen Whittock asked me if I knew the answer and I said 'yes' … I said something like, 'yes, he is right, it's googol'."

He added: "The major did plump for googol and of course the rest was history, he'd won the one million pounds on the evening."

'Very, very strange'

So, how suspicious was Mr Thomson at the end of the quiz?

He said: "I thought there was something, not deceitful or dishonest, but something very very strange was unfolding before my eyes."

On the ITV drama he said: "From my perspective, in light of the fact that they were convicted, I thought it probably lent or portrayed Major Ingram and his wife rather too sympathetically."

He added: "Obviously at the end of the drama it says they are considering an appeal which, you know, after 19 years, why not?"