Kate Middleton once again proved that she deserves to be the partner of the future king.

The Duchess of Cambridge was a picture of confidence and grace as she assisted Queen Elizabeth in welcoming NATO leaders to a reception dinner at Buckingham Palace.

On Tuesday evening, Kate Middleton helped her grandmother-in-law Queen Elizabeth II entertain the leaders of the most powerful countries in the world, including U.S. President Trump. Kate came without Prince William, who is currently in Kuwait and Oman for his royal tour.

The royal reception was to celebrate the 70th year of NATO. Kate was joined by other senior members of the royal family, including Prince Charles and Camilla, Duchess of Cornwall. 

Where's Meghan?

Yet, another notable absence was that of Prince Harry and wife Meghan Markle. The Duke and Duchess of Sussex are currently on leave for their much-needed family time. The news of their six-week leave from royal duties came when Meghan was caught in the middle of a controversial interview.

The intense scrutiny she received from the British Press has gotten to her. In the candid interview with ITV, Meghan talked about how she is struggling since she married into the royal family. The first two years were quite tough for the former "Suits" actress. Not only did she need to adjust to the royal life, but she also welcomed their son, Prince Archie -- and that meant a lot of changes.

Meghan and Harry would also be skipping the annual Holiday celebration at Sandringham. 

The reception dinner at the palace was the central showpiece in a series of meetings for two days. The NATO alliance was established in 1949 with only 12 members, but today, it has evolved into a defense agreement among 29 member countries.

The United Kingdom was one of the founding members of the NATO alliance. London was the home to its first headquarters. 

The Next Queen

Kate Middleton chose a bright green ensemble to celebrate the occasion. She chose to wear her hair down, exuding a simple yet elegant look that is perfect for the occasion.

Multiple sources from the palace told PEOPLE that Kate has become more confident over time. Besides her role as a mother to her three young kids and wife to Prince William, Kate has also found passion in reaching out to mothers and children everywhere.

A trusted source from the palace said that the Duchess of Cambridge is slowly finding her voice. 

Prince Charles and Camilla were also there with the Queen. They formally received the NATO leaders and their partners in the palace. Moreover, they took a formal photograph with the rest of the royals and the various heads of governments and states. 

Kate was with the company of the other royal members of the family, including Princess Anne, Prince Edward and Princess Alexandra.

Notable was the absence of Prince Andrew, who had recently stepped down from his royal duties and public life. His controversial friendship with convicted sex offender Jeffrey Epstein has put him in hot water. 

Kate graciously welcomed the guests in the staterooms in the palace. She was seen talking to some of them. Indeed, she looked like she is up for the challenge of becoming the Queen Consort in the future. 

READ MORE: Kate Middleton Will Never Take Queen Elizabeth II's Place -- Here's Why!