Tom Jones. [Photo/Agencies]

Sir Tom Jones believes Britain's Prince William and Duchess Catherine have the "ingredients" to succeed at marriage.

The 'What's New Pussy Cat?' singer - who has been married to wife Melinda for 55 years - admits he thought of the royal couple's nuptials at London's Westminster Abbey in April 2011 as a "fairytale" and thinks they will have a long and happy union.

He said: "The wedding really was a fairytale and the fact it was so popular worldwide shows how much our royals affect people.

"Everyone was affected by the pageantry of the occasion, but ultimately it was great to see two lovely young people in love. You can never know if a marriage will last, but they've got the ingredients to succeed."

Tom has met Queen Elizabeth before, and admits he was worried she would send him to the Tower of London when he revealed he lived in Los Angles instead of the UK.

He said: "Before one of the Royal Variety Performances, she asked me I liked living in America. I said I only lived there because it was more convenient, rushing my words out as if Her Majesty could still send me to the Tower!"