Prince William knows all about the ''fear'' of fatherhood.

The 36-year-old royal - who has Prince George, five, Princess Charlotte, three, and Prince Louis, nine months, with his wife Duchess Catherine - openly discussed the struggles of becoming a dad and the ''fears'' of having a newborn baby around.

During a visit to a 'Future Dads' session, which helps to provide practical guidance and advice for fathers-to-be, he said: ''The fear of having a newborn baby, that's very vulnerable and that's what you spend most of your time worrying about, thinking what do I do? And that's the thing isn't it? It's very daunting of how tiny they are when they first arrive. They are so fragile and everything's so tiny, their little fingers and toes, you do feel like if you move them around too much they're going to break almost but they don't!''

The Duke of Cambridge met with Rick Karadia-Hudson, who was attending the sessions ahead of the arrival of his first child in May, and Prince William drew on his own experience and quipped that it only got more hectic the older the child got.

When Rick said ''they move about so much'', the Prince joked back: ''Wait 'til they're nine months, then they're off. You've got one leg and one arm!''

Meanwhile, Duchess Catherine had previously admitted her husband had struggled with fatherhood as she spoke to single father Billy during a visit to Hornsey Road Children's Centre in north London.

Speaking about their meeting, Billy said: ''She said he did not know exactly what to do ... She was saying William was sort of similar and I just wanted to let her know how Family Action have been there for me and I think they need more support.''