A children’s book illustrator who sexually assaulted a young girl at a play area in Gospel Oak has been jailed.

Henry Christopher Mendes, 65, of Park An Pyth, Penzance, pleaded guilty to two counts of indecent assault relating to crimes involving two different girls during the 1970s.

Mendes was known to the families of both victims who were under the age of 10 at the time of the assaults.

The first incident occurred in August 1977, when he was visiting the victim’s parents in north London. He asked the victim to walk with him to the local off-licence, offering her an ice cream as an incentive.

Walking back to her home in the dark, Mendes forced her to perform a sex act while in the Lismore Circus children’s play area.

On returning home they were met by the victim’s worried mother, as her daughter had been gone a long time. The victim did not disclose to anyone what had happened to her, until much later.

The second offence happened between 1976 and 1978 in north London.

One night the victim was in bed, when she became aware of a man standing next to her, breathing in a heavy and laboured way. She heard him say “you’re so beautiful” and she recognised the voice as that of Mendes. She stayed still, hoping he would go away, but he attempted to sexually assault her. He stopped because another man called out for him from outside the bedroom.

In 2013, the victims reported the incidents to police. Mendes was identified, arrested and interviewed.

During the course of the investigation, his computer was found to contain nearly 400 indecent images of children.

He pleaded guilty to two counts of indecent assault, seven counts of making indecent photographs of a child, and one count of possession of extreme pornographic images.

He was sentenced at Blackfriars Crown Court on Friday to three years and nine months imprisonment.

One of his victims, wishing to retain anonymity, said: “One of the things I would like to add is how well treated I have been by the Met Police.

“It has taken a long time to feel brave enough to come to the police with this, not only confronting what happened within myself but also having to tell a total stranger. I would have no hesitation in recommending that anyone who has experienced any type of abuse report it, in fact I would urge them to. It might be scary at first but personally speaking it was a cathartic experience that has really helped me to process what happened to me. I have no idea how they do such a difficult job and do it so well, pure professionalism.”

Officer in the case, detective constable Jo Dell of the Sexual Offences, Exploitation and Child Abuse Command, said: “I would like to thank both victims for their bravery in reporting these incidents to police and their ongoing support throughout the investigation. They have shown resilience which enabled the case to proceed to this successful conclusion. Mendes is a serial offender who has abused the trust of his friends and targeted vulnerable young girls.”

Detective inspector Neil Smithson, of the Sexual Offences, Exploitation and Child Abuse Command, said: “I would appeal to any other victims of Mendes to come forward – the Metropolitan Police will fully support you and seek to bring offenders to justice, no matter when the offences were committed.”