Who Wants To Be A Millionaire? host Chris Tarrant has told a court of his shock when he heard that a contestant was suspected of cheating his way to the top prize.
Chris Tarrant arriving at court
The presenter said he would not have signed the £1m prize cheque if he thought Major Charles Ingram had not been "playing by the rules."
Mr Tarrant, who was giving evidence on the fourth day of a trial at London's Southwark Crown Court, said he had been "elated" by the major's success.
Mr Ingram, 39, is accused of being guided to the right answers by coughing signals from an alleged accomplice, Tecwen Whittock.
The major and his 38-year-old wife Diana, from
Easterton, Wiltshire, deny conspiracy to "dishonestly procure the execution of a valuable security" in September 2001.
Mr Whittock, 53, who lives in Cardiff, and is head of business studies at Pontypridd College, south Wales,
denies the same charge.
Mr Tarrant said he had not noticed coughing during the show because there was a lot going on - "loud applause ... extraordinary behaviour, exciting behaviour, very hard to follow behaviour".
Mr and Mrs Ingram deny the charges
But watching a recording afterwards he had noticed a pattern of coughing.
Mr Ingram's behaviour had been "eccentric" as he took a long time to answer every question.
But when production staff told him there were suspicions about the win, Mr Tarrant said: "I could not believe it. I did not want to believe it.
"You don't expect someone to come on a show like that and cheat."
The court also heard from contestants who - like Mr Whittock - were eliminated in the "Fastest Finger First" section of the show.
James Thomson and Thomas Lucy, who sat either side of Mr Whittock said they did not notice him coughing during the major's appearance.
They seemed as normal as people who had just won £1m would be in that situation
But Stephen Carroll said the father-of-three was coughing "more or less all the way through" and audience member Susan Saunders recalled thinking Whittock had a "terrible cold".
Mr Whittock claims his cough was caused by an allergy.
After the show ended Mr Tarrant visited Mr Ingram in his dressing room to congratulate him and his wife.
"They seemed as normal as people who had just won £1m would be in that situation," he said.
Cross examined by Sonia Woodley QC, the presenter said the atmosphere in the studio was "huge" after the win.
Ms Woodley said: "You were delighted for him and it made great television," to which Mr Tarrant replied: "Absolutely true."
The quiz show host also revealed how he does not know the correct answers to the questions until contestants give their final answer.
A signal then appears on his screen and he demonstrated for the judge how he tries to keep a "strange impassioned" face so as to not give away the answer.
The producers of the show, became suspicious after the recording and called the police.
Celador withheld the £1m and decided not to broadcast the episode featuring Mr Ingram.
The trial restarted on Friday after a juror fell ill. It is expected to last four weeks.
Mr Ingram has launched civil proceedings to recover the £1m.
The trial continues.