An "insidious" paedophile, who encouraged his partner’s children to watch the couple have sex before sexually abusing them, has been jailed.
The 61-year-old from King's Cross in central London was described by prosecutors as the driving force behind the abuse.
After he pleaded guilty to abusing the children throughout the full course of their relationship he finally sentenced to six and a half years behind bars at Blackfriars Crown Court.
The mother, who previously pleaded guilty to her involvement, will be sentenced in November.
The children have since been taken into care.
The mother told police the assault began when the family shared a room on a holiday in Spain.
The couple began to behave intimately in front of her children, which then moved on to involve the young boy and girl. The abuse escalated as the children were forced to participate more.
Sentencing the abuser, Judge HHJ Mathieson said: “This was grooming behaviour of the most insidious and calculating type over months and years."
Tetteh Turkson, from the CPS, said: “The normal boundaries that keep children safe and separate from adult sexual activity were broken by these adults. This man was the driving force behind the involvement of the children in the sexual activity taking place. These incidents occurred whilst he was in a relationship with the children’s mother.
“They occurred because this man derived sexual gratification from involving the children in adult sexual activity. The prosecution case included video interviews from the two young victims and their mother who owned up to her actions and will also face justice. This case is unusual and disturbing and I am pleased that justice has been done. I hope the victims can now work towards coming to terms with what has happened.”
The man, who remains unnamed to protect the identity of the children, was jailed on two counts of causing or inciting a child under 13 to engage in sexual activity, two counts of engaging in sexual activity in the presence of a child, and one count of sexual assault of a child under 13.
The mother has already pleaded guilty to two counts of engaging in sexual activity in the presence of a child and one count of sexual assault on a child under 13 on two occasions between December 2014 and March 2019.