A former Dragons' Den star paid a 13-year-old schoolgirl to be his sex slave after meeting her on a "sugar daddy" website, a court heard.

Doug Richard, 57, allegedly spanked the girl's bare bottom repeatedly before having sex with her in a pre-booked room in London.

The court heard that he gave the alleged victim and her 15-year-old friend £480 in cash and PayPal deposits, including the train fare to travel from Norwich to the capital to meet him.

The millionaire, of Islington, north London is accused of three counts of sexual activity with a child, one of causing or inciting a child to engage in sexual activity and a charge of paying for sexual services.

He denies the charges, insisting the sex was "consensual" and that he "reasonably believed" the alleged victim was aged 16 or over while the money was not for sex but to help with travel expenses.

Prosecutor Gino Connor told an Old Bailey jury that Richard met the girl through an American website called Seeking Arrangements.

Richard listed his profile as a "sugar daddy" while the 13-year-old girl called herself a "sugar baby", jurors were told.

Deleted iChat recovered from the defendant's Apple MacBook air revealed how Richard suggested they meet after school in December 2014 as he found weekends difficult.

He asked her for a sexy photograph with "less clothing more revealing positions", Mr Connor said.

He instructed her to pose on her hands and knees for a selfie, saying: "I'm now officially horny".

She told him she was doing it "now" saying: "You are my new daddy I will do anything to keep you happy."

When she asked about what kind of punishment he would give her, he told her that he wanted to "paddle her arse until it's bright red", jurors were told.

They went on to arrange to meet in London and the defendant made a payment of £120 through PayPal on New Year's Eve.

The 13-year-old travelled with a 15-year-old friend to Liverpool Street Station on the morning of January 2 last year and met Richard at a nearby cafe.

When asked how old they were, the girls told him they were 16 and 17, Mr Connor said.

According to a statement by the older girl, they went to a hired apartment in Bishopsgate where Richard asked her if she wanted to be his "slave".

When she declined, he allegedly told her that her friend had told him she wanted to be "someone's slave".

The 15-year-old girl told police that she had informed Richard that she was not into sex and she pulled away when he kissed her using his tongue, describing it as "horrible and smoky".

The 13-year-old girl then took off all her clothes and undressed Richard before he instructed her to get on her hands and knees in front of him.

The girl said she would rather be spanked and lay across his lap, the court heard.

He spanked her seven times before ordering her to perform a sex act on him, the court heard.

The defendant took the alleged victim to bed and asked her friend if she wanted to watch but she declined, jurors were told.

The girl told police that she did not see what happened in the bedroom but she could hear the "bed rocking" and her friend complain that it hurt.

Five minutes later, she went into the room and saw the 13-year-old girl perform another sex act on Richard, Mr Connor said.

Afterwards, Richard gave both girls £60 and called them a taxi so they could go shopping at American Apparel before heading home.

Later that night, the 15-year-old tried to extract more money from Richard who asked her if she would consider coming to London again for sex.

She told him: "I'm not in for sex but money," the court heard.

Police were alerted after the mother of the older girl noticed a PayPal deposit in her bank account.

An examination of the 13-year-old on January 4 indicted she had suffered some sort of injury which could have been caused by sex.

Richard was arrested on January 5 last year at the Lord Milner Hotel in south west London.

He reacted by saying: "As you can see I am in a lot of trouble."

While getting dressed, the American businessman who was once an adviser to Prime Minister David Cameron, added: "Can I ask you a question, a hypothetical question. What if I thought she was over 16 but she was in fact under 16?"

When advised by an officer to discuss it with his lawyer, he added: "Under 16. Wow."

The trial is expected to go on for four days.