A man accused of grabbing the flag on Queen Elizabeth II's coffin wanted to check for himself that she was indeed dead, a London court heard Tuesday.

Queen Elizabeth's casket lay in state in London's Westminster Hall from Wednesday until Monday ahead of her state funeral, with an estimated 250,000 members of the public queueing for hours to file past the coffin and pay their last respects.

Muhammad Khan, 28, allegedly rushed up to the coffin and grabbed the Royal Standard on Friday night.

He was arrested and appeared at Westminster Magistrates Court on Tuesday, charged with two public order offences.

"The defendant had reached Westminster Hall. He was then seen by officers, who were present, to approach the coffin," prosecutor Luke Staton told the court.

"He stepped off the carpet in the direction of the catafalque, then grabbed hold of the Royal Standard flag draped over the coffin with both of his hands."

Khan was quickly detained, arrested and interviewed by police, the court heard.

"The defendant did express the idea that the Queen is not dead and that he approached the coffin because he wanted to check for himself," Staton said.

The court heard that Khan was suffering from delusions.

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District Judge Michael Snow told him: "At the time when you were in Westminster you didn't accept that the Queen was dead and that was the reason you were moving towards the coffin to satisfy yourself that she was."

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He added: "He is delusional still and thinks the Queen is not dead, thinks King Charles has something to do with it."

The judge granted Khan bail on condition that he remains in an east London mental health hospital until his next appearance at the same court on October 18.

Last week, Adio Adeshine, 19, was remanded in custody charged with two counts of sexual assault after allegedly exposing himself in the queue and pushing into mourners from behind.

Adeshine is alleged to have plunged into the River Thames in an attempt to evade police before being arrested.