The 2 best photos of the Queen and Prince Philip, according to a royal photographer

• Royal photographer Samir Hussein photographed Prince Philip for 15 years.
• Hussein shared his two favorite photos of the duke and Queen Elizabeth with Insider.
• The photos show the couple's "relaxed partnership" and Philip's sense of humor.

The Queen and the Duke of Edinburgh were married for 73 years before he died at the age of 99 on April 9.

As the longest serving British consort, Prince Philip accompanied Her Majesty to numerous royal engagements across the UK and the world.

One person there to witness these engagements was royal photographer Samir Hussein, who photographed the duke for 15 years.

Hussein spoke to Insider about his favorite memories of the late duke.

Hussein's favorite photo of the Queen and Philip showed their 'relaxed partnership'

"Having photographed the Duke of Edinburgh for the past 15 years it really hit home when news broke of this death," Hussein told Insider. "I was soon reminiscing and digging out historical and poignant photos of the duke from more happy occasions."

Hussein says his favorite photo of Philip and the Queen was taken at the Epsom Derby in 2009, a horse racing event in England.

He described the couple as "standing on their own away from everyone else watching the horses in the parade ring."

"They stood having a chat and smiling with each other, totally in tune and relaxed as a partnership, producing this lovely picture," he added.

Philip's sense of humor was one of the main reasons why Hussein enjoyed working with him. The photographer described the royal as "a very witty man" with a "sense of mischief."

"Clearly he was a man of great devotion and dedication, but you still never really knew what might happen with the duke. Whenever I think of my best pictures and my fondest memories of him it involves his humor," Hussein said.

One of these pictures was taken during Royal Ascot in 2012, when Hussein captured the moment Philip and the monarch arrived by carriage.

"As they were arriving in the parade ring in front of a large crowd, the duke leaned in to the Queen and said a few words before bursting into uncontrollable laughter," Hussein said. "The Queen was also grinning, so it produced a great photo as they passed in front of me."

"This was typical of the impulsive humor the duke could produce in front of the camera," he added.

It's thought the Queen was discouraged from marrying Philip because of his sense of humor, as Insider's Amanda Krause previously reported.

The Queen's courtiers reportedly argued that Philip was "entirely the wrong person to choose" because he made so many "gaffes" when the couple got engaged.

Nonetheless, the couple went on to wed at Westminster Abbey in 1947.

They have four children, eight grandchildren, and 10 great-grandchildren, two of which were named after Philip.

The couple's granddaughters Zara Tindall and Princess Eugenie gave their newborn sons the middle name "Philip" just weeks before he died.