A former Dragons' Den star has admitted engaging in a Fifty Shades of Grey role play fantasy with an under-age girl he met on a sugar daddy website.

Doug Richard, 57, is on trial at the Old Bailey accused of having sex with and spanking the 13-year-old girl after she travelled to London with a friend to meet him in January last year.

Giving evidence in his defence, the married father-of-three insisted he would never "knowingly have sex with a child" and he now felt "terrible" about what happened.

The American millionaire told jurors that he had used the sugar daddy website Seeking Arrangements for around four years and had gone on to meet some women in their 20s for sex.

He said: "As mortifying it is to say, I was looking for role play and fantasy relationships involving dominance and submission."

Richard told jurors that he kept his activities on the site secret for "obvious reasons " adding: "It bothered me but I was also quite addicted to it."

The entrepreneur first messaged the 13-year-old girl after being attracted by her profile describing herself as "submissive".

He said: "It's Fifty Shades of Grey-type stuff. I said 'it seemed like we have something in common are you interested' and she replied 'yeah a lot, I'm extremely interested'."

Asked if she had "prior arrangements" she told him that other men had purported to be dominant but they had "disappointed" her, he said.

On her age, Richard said: "You cannot sign up on the site unless you are 18. I just assumed and her profile said 18."

He told the court he got the impression she was sexually experienced during online chat and she sent him a nude photograph of herself in a "full frontal" pose.

When they arranged to meet, Richard told jurors he offered to pay for her train ticket and taxi fare but their relationship was never about money.

He said: "What we were talking about was what we wanted to do which was to have a Fifty Shades of Grey role play between us and that's all we ever talked about."

Richard went on to describe meeting the girl and her 15-year-old friend at a cafe before heading off to a pre-booked apartment near Liverpool Street station.

Before they arrived, he said the alleged victim had discussed Cosplay - when a woman dresses to look younger - and her wish to go to a fetish club called Torture Garden.

Richard admitted that he did engage in various sexual acts, including spanking the girl, but disputed her 15-year-old friend's evidence that she witnessed some of it in the living room.

He told jurors that he took the 13-year-old into the bedroom after the older girl told him she was not interested in being a "slave".

Sarah Elliott QC, defending, said: "There are four different sexual activities on the indictment. Do you accept those four sexual activities took place?"

Richard replied: "Yes I do. They took place in the bedroom."

He denied the girl ever appeared to be upset or hurt, saying: "This is all about role play and fantasy and having fun. If it's not fun I would have stopped."

On why he gave the two girls £120 as they parted, he explained: "I was trying to be very sugar daddy. It was a gift basically. I was trying to be nice so I gave them some money to go shopping."

Richard said his arrest days later was "as serious as anything that happened to me in my life".

Asked how he felt about what happened now, he said: "I feel terrible. I feel terrible for her and I feel terrible about myself. I feel terrible for my wife and children."

Ms Elliott asked: "If you had known at the time she was not above the age of consent, what would you have done?"

Richard replied: "I would not have had anything to do with it."

The defendant added that he was now trying to address his "addiction" with therapy.

He told the court that the reputation of his School for Startups business initiative which brought him into contact with the British Government had been "shattered".

Richard, of Islington, north London denies 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.

Later, prosecutor Gino Connor quizzed the defendant about his online chat with the girl in which she told a "pack of lies" about being aged 17 and a 34C bra size - as opposed to 13 and a 32A.

He said: "What I'm going to suggest to you is this exchange and the fact you say you had seen her naked with full frontal nudity indicated to you she was a young, immature girl.

"A man of your experience must have appreciated either when you saw the picture or when you first met her that she was not 17 years old."

Richard replied: "I absolutely thought she was 17. We had long, elaborate sex chats. She sent me a photo of her naked.

"None of these raised the alarm and had they raised the alarm I would have been horrified. I'm horrified now."

Mr Connor suggested his "addiction" to his activities on the sugar daddy website had been "out of control".

The defendant replied: "I cannot say."