Simon Cowell was worried he was going to miss his son's birth.

The 'X Factor' boss got a call from his partner Lauren Silverman to say their baby was on his way, and he faced a 15 hour journey to make it in time to be with her for Eric's arrival yesterday (14.02.14).

An insider told The Sun newspaper: ''It was a very emotional experience for him - but his overwhelming emotion now is relief.

''He knows he was cutting it very fine to get back and wouldn't have forgiven himself if he had missed the birth. Obviously his number one priority at the moment is the health of his son and Lauren.

''He's so delighted that everything is OK. He's still getting his head around the fact that he's now a dad and has been texting family members and close friends.''

Although he's typically calm and in control, Simon is said to have lost ''his cool'' when he received Lauren's call, but she ''knows the signs'' and gave him enough time to arrive by her side.

A friend said: ''Simon was in shock when he got the call. It's not often he loses his cool but this was one of those times. Even though he didn't want to see the birth, there was no question that he'd wouldn't be at Lauren's side.

''She has had a difficult pregnancy so her health is his priority. This is Lauren's second baby so she knows the signs - she gave him as much time as humanly possible to get there.

''When he arrived in New York she was in the advanced stages of labour.''