The Notting Hill and Bridget Jones star is "thrilled" to have welcomed a baby boy, a brother for his one-year-old daughter Tabitha, with Chinese actress Tinglan Hong - a relationship that started out as a fleeting affair".
The 52-year-old film star has almost been more famous for his appearance at the Leveson Inquiry and his campaigning for a more responsible press of late than for his films, and his tweets are not without a reference to that passion.
He tweeted: "In answer to some journos. Am thrilled my daughter now has a brother. Adore them both to an uncool degree. They have a fab mum.
"And to be crystal clear. I am the Daddy.
2Thanks for v kind messages. Now I've confirmed (press somehow got birth certificate & were calling),hoping my family will be left in peace."