Princess Kate dazzles in Princess Diana's tiara at state banquet with Spanish royals

— -- Prince William, Princess Kate, and Prince Harry attended the lavish state banquet at Buckingham Palace hosted by Queen Elizabeth for King Felipe and Queen Letizia of Spain tonight.

Kate wore Princess Diana's favorite Cambridge Lovers Knot Tiara and borrowed jewels from Queen Elizabeth. The queen's spectacular ruby and diamond King George VI and Queen Elizabeth Bandeau Necklace with a diamond pendant was last believed to have been worn in the 1980s. She also accessorized her blush pink Marchesa dress with glamorous pearl drop earrings that appear to be the same ones worn by Princess Diana on many occasions. The Cambridge Lovers Knot Tiara was a wedding gift to Diana. Kate first wore the tiara at the diplomatic reception in 2015 and the state dinner in 2016.

Queen Elizabeth wore a stunning Brazilian aquamarine and diamond tiara and necklace. Queen Letizia also donned a glamorous tiara and a vibrant off-the-shoulder red gown, the country's national color.

The menu consisted of poached filet of salmon with fennel in white wine sauce, medallions of Scottish beef with truffles in a Madeira sauce, fondant potatoes, and chocolate and raspberry tarts.

The black-tie dinner included about 170 guests in the Buckingham Palace ballroom.

The Spanish royals had been postponed from June due to the election in the U.K. called by Prime Minister Theresa May.

It was Prince Harry's first state banquet as he takes an increasingly more high profile role as Prince Philip dials back. Philip was making his final ceremonial engagement with this state banquet before his retirement starts this fall. He made the most of it, enjoying the carriage ride back to Buckingham Palace with Queen Letizia while Queen Elizabeth traveled with King Felipe. Following the festivities today, Prince Philip has two additional events scheduled next week, one at the Canada House and another at the Royal Geographical Society.

Earlier in the day, King Felipe and Queen Letizia were met by Prince Charles and Camilla, the Duchess of Cornwall, at a hotel and then escorted to Horse Guards for an official ceremonial welcome by Queen Elizabeth and Prince Philip.

The visit is an important component of the royal family's Brexit charm offensive to solidify the relationship with the Spanish as the U.K. negotiates its exit from the European Union.

Queen Elizabeth told banquet guests, "This state visit is an expression of the deep respect and friendship that describes relations between Spain and the United Kingdom. Just occasionally, a state visit can provide an opportunity for great personal happiness also. So it was, more than a century ago, when your great-grandfather, King Alfonso the Thirteenth, met his future wife, Princess Victoria Eugenie, the grand-daughter of our Queen Victoria, in this very ballroom."

Queen Elizabeth spoke about the importance of the shared history between the two countries in her remarks.

"The relationship between our two nations is dynamic and modern. We are NATO allies, striving together to improve security in Europe and across the globe."