King Charles III and his son Prince William made a surprise appearance Saturday for the mourners lined up in an hours-long queue to see Queen Elizabeth II’s coffin.

People from all over the world have joined the line that extends some 7 miles from the Palace of Westminster to Southwark Park in southeast London with authorities warning the wait could take more than 16 hours. 

But the Royals brought some much-appreciated encouragement to the mourners who lined the chilly River Thames, many of whom apparently spent the night outside to hold their spots in line. 

Prince William was heard speaking and joking around with the people in line and offered them words of support, telling them they were more than halfway there. 

King Charles III shakes hands with mourners waiting to pay respects to Queen Elizabeth lying in state

King Charles III greets members of the public queueing to see the lying in state of Queen Elizabeth II along the river Thames at Lambeth. on Sept. 17, 2022 in London. (Karwai Tang/WireImage)

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The newly appointed prince of Wales stopped to speak with several children and asked them if they were warm enough.

Prince William

Britain's William, Prince of Wales greets people, while they queue to pay their respects to Britain's Queen Elizabeth, following her death, in London, Sept. 17, 2022.  (REUTERS/John Sibley)

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He told mourners that his grandmother would not have believed the level of support she has received following her death on Sept. 8.

The prince spoke with and thanked women in line who had traveled from Peru to pay their respects to the queen. 

The king’s appearance was also a hit and received three cheers of "hip-hip hooray" upon his arrival along with periodic unified calls of "God save the King."

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King Charles III left before his son.

Prince William mourners

Britain's William, Prince of Wales greets people in line to pay their respects to Britain's Queen Elizabeth following her death, in London, Sept. 17, 2022.  (REUTERS/Phil Noble)

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Both men were surrounded by large swaths of security guards who encircled the royals as they walked along the Thames with their supporters.

The king and prince left in separate cars waiving and thanking the crowds of people. 

Prince William and his brother Prince Harry are set to stand vigil over the queen's coffin Saturday afternoon.