The prince told journalist Robert Hardman that the queen's children and other family members have not had much luck. Hardman's book, "Our Queen," is running in installments in the Daily Mail.
"She's so dedicated and really determined to finish everything she started," William said in the installment published Saturday. "She'll want to hand over knowing she's done everything she possibly could to help, and that she's got no regrets and no unfinished business; that she's done everything she can for the country and that she's not let anyone down -- she minds an awful lot about that."
William said his grandmother was very helpful before his wedding to Kate Middleton, when the royal staff presented him with a list of hundreds of people to invite.
He called the queen: "I rang her up the next day and said: 'Do we need to be doing this?' And she said: 'No. Start with your friends first and then go from there.' And she told me to bin the list. She made the point that there are certain times when you have to strike the right balance."
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