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Prince William prepares for final pilot shift ahead of full-time royal duty - ITV News
His installation as a full-time royal will coincide with grandfather Prince Philip's retirement from public engagements.
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Personally, I've always thought this was the general plan-to have William and Kate become more active only when the senior (older) royals began to step back.
I believe the "gap year" William had after he left the RAF was partly the result of all the ill health Philip, the Duke of Kent and Princess Alexandra suffered from in 2013. I don't think the Way Ahead Group wanted William to have any firm commitments so he could step up if needed.
Remember, Philip fell ill, had surgery and disappeared for awhile. I have my suspicions about what was going on. I think they all weren't sure how much of a recovery Philip would make and wanted William available if needed.