The 63-year-old actor has agreed to give financial assistance to Maria Shriver – who he separated from last month, shortly before it was made public that he had fathered a child with their former housekeeper Mildred 'Patty' Baen – for their younger children Patrick, 17, and Christopher, 13, despite neither party filing for divorce yet.

A source told “[Arnold is paying] a significant amount of child support. Arnold is also paying for his sons, Patrick and Christopher's private school bills.

“Even though Maria is a Kennedy, and has inherited a great deal of money from her parent's estate since their deaths, she is taking the child support. Under California law she is entitled to the child support, once either one of them files for divorce. Maria and Arnold's lawyers have been working on a divorce settlement but in the meantime Arnold is willingly paying the money to Maria."

Insiders claim Maria – who also has daughters Katherine, 21, and Christina, 19, with the former Governor of California – has enlisted the help of forensic accountants to get an accurate view of her estranged spouse's assets in order to ensure their divorce is fair.

The source added: "Maria wants to get a fair divorce settlement, and move on with her life. She has already begun to do so."

Despite the revelations that emerged after the split, the sources claim the separation is far from acrimonious, with Maria particularly keen for the breakdown of her marriage not to impact too much on their children.

The insider said: "She and Arnold talk quite often, it would surprise people how gracious Maria is being about the entire situation. Maria doesn't want the kids to suffer because of stupid decisions their father made, and she encourages them to be honest about their feelings. Arnold has made tearful apologies to his children for his indiscretions."