The Love Actually star took to Twitter.com to inform fans of her and actor husband James Thornton's baby joy, writing, "So happy! Kit James our baby boy was born yesterday at 4:14pm weighing 8lbs! He's beautiful!"

Thornton also expressed his glee on the microblogging site, posting, "Got the best April Fool ever yesterday! Our baby boy Kit James arrived into the world! He's a big lad, 8lbs. Mum and baby both fine."

The couple, who already share a two-year-old daughter, Eva, married in 2003 after working together on the BBC TV adaptation of Charles DICkens' David Copperfield.