The line for members of the public to view the late Queen Elizabeth II's coffin was approximately 4 miles long by Thursday afternoon, according to the U.K. Department for Digital, Culture, Media and Sport.

A mother holding her baby was among the thousands of mourners waiting for hours to pay their respects.

The late monarch is lying in state at London's Westminster Hall until her funeral on Monday.

William, Prince of Wales, and Kate, Princess of Wales, are in Sandringham on Thursday to view the tributes to William’s grandmother, Queen Elizabeth II.

King Charles III wants to protect the planet for future generations -- a passion he has highlighted throughout his decades as monarch-in-waiting.

Now, Charles ascends the throne as the longest-serving Prince of Wales in British history. And in those six decades, he not only voiced his concerns about the destructive processes that are harming the Earth but implemented sustainable, organic practices in his own homes.

"His mother took the crown at a very young age, and nobody knew what she stood for," David Victor, a professor of innovation and public policy at the University of California at San Diego's School of Global Policy and Strategy and author of "Fixing the Climate: Strategies for an Uncertain World," told ABC News. "Whereas he is taking the crown very late in age, and everybody knows what he stands for -- and for a whole range of topics."

A royal guard apparently fainted as he watched over the coffin holding the late Queen Elizabeth II at London's Westminster Hall.

The incident was captured on BBC News' live streaming broadcast early Thursday at around 1 a.m. local time. A guard, who was standing at the foot of the coffin, appeared to faint and fall to the ground.

BBC suspended its livestream following the incident.

Guards clad in ceremonial uniform are maintaining a 24-hour vigil around the coffin inside Westminster Hall.