The second-in-line to the throne is expecting his first child with wife Duchess Catherine and father-of-three Noel says if William wants some peace and quiet, he would be better off fighting for his country because the baby will take up a lot of the couple's time and ruin his chances of sleep.
Speaking at a press conference to announce the line-up for the 2013 Teenage Cancer Trust concerts, the former Oasis guitarist said: ''They're not the first people in the country to have a child, are they? I've got three, you know. Do I have any advice for them? People write books about that sh*t. Very expensive books - my wife's got 'em all.
''Tell William he'd be better thinking about rejoining the army - he'd have a quieter life.''
However, William - who works as an RAF search-and-rescue pilot - wants to be hands-on father and could even scale back on his work once the tot arrives.
A source told The Sun newspaper: ''William cannot wait to be a dad. He wants to have the family stability for his heir that he never had. He will even change nappies. He's a modern man.''
Duchess Catherine - who is also known as her maiden name of Kate Middleton - is currently in hospital suffering from hyperemesis gravidarum (acute morning sickness).