 -- Princess Kate's closest adviser, Rebecca Deacon, is planning to depart Kensington Palace this summer.

Deacon serves as Kate's private secretary, which is the equivalent to a chief of staff. Deacon has long been a trusted member of Kate's staff and is by her side at nearly every public engagement she attends.

Kensington Palace announced Deacon's planned departure in a statement.

"After a decade of service to The Duke and Duchess of Cambridge and Prince Harry, Rebecca Deacon will be stepping down as Private Secretary to The Duchess of Cambridge,” the statement read. “She plans to leave the household in the summer. Their Royal Highnesses are incredibly grateful for all the hard work and support Rebecca has provided over the past [10] years, and wish her well in the next phase of her career.”

Deacon's duties as Kate's private secretary include briefing Kate, accompanying her to engagements, contributing to speeches and organizing Kate's schedule. She also routinely interacts with the charities for which Kate, 35, serves as royal patron.

Deacon was recognized for her work in helping to plan the Concert for Diana in 2007. The concert, led by Prince William and Prince Harry, was held in London on what would have been the 46th birthday of their late mom, Princess Diana.

She later served as press secretary for Harry's charity, Sentebale, before moving to Kate's private office in 2012.

Deacon recently announced her engagement. In a rare move, due to the enormous respect William, Kate and Harry have for Deacon, her wedding will reportedly take place at the Chapel Royal in St. James Palace, where Prince George was christened. William and Kate are expected to attend the wedding.

It is unclear what's next for Deacon, who is highly regarded by the royal family and the royal press corps.

Kensington Palace has not yet revealed who will fill the private secretary role once Deacon departs.