Hundreds of anti-monarchy protesters have gathered in central London’s Trafalgar Square, just a mile away from Westminster Abbey where Charles will be crowned.

Their chants of "not my king" were met with boos from others in the crowd who are fans of the royals.

-ABC News' Ibtissem Guenfoud and Patrick Reevell

Charles’ coronation is the first since 1953, when his mother was crowned.

The queen’s coronation also took place at Westminster Abbey, where every coronation service has taken place since 1066.

Over 8,000 guests filled the abbey for Elizabeth's coronation, including Charles, who was 4 at the time.

One famous photo shows Charles resting his head on his hand as he stands between his grandmother, Queen Elizabeth The Queen Mother, and his aunt, Princess Margaret.

Wearing suits, fascinators, military uniforms and medals and religious clothing, guests began filing into Westminster Abbey Saturday over three hours before the start of Charles’ coronation service.

Actress Emma Thompson and singer Lionel Richie, who is performing at Sunday's coronation concert, are among the guests.

Watching the coronation service in-person are over 2,200 invited guests who represent over 200 countries, according to Buckingham Palace.

In addition to royal family members, the assembled guests include heads of state, members of foreign royal families, representatives from charities of which Charles and Camilla are patrons, faith leaders, Nobel Prize winners and members of the Diplomatic Corps.

Just as with royal weddings and funerals, Charles’ coronation is expected to be viewed by millions of people around the world.

Cameras are allowed inside Westminster Abbey, so everyone at home will get a chance to see the biggest moments of the day.

ABC News, "Good Morning America" and ABC News Live will have special coverage of the coronation on Saturday, May 6, from 5 to 10 a.m. ET.

The five hours of special coverage will also be available to stream on ABC News' digital platforms, including ABCNews.com and GoodMorningAmerica.com, mobile apps, social platforms and over-the-top (OTT) services.

ABC News Live will also immediately re-air the five hours of coverage from 10 a.m. to 3 p.m. ET on Saturday, May 6.

William pays homage to his father on behalf of the royal family, following an homage from the Archbishop of Canterbury on behalf of the Bishops of the Church of England.

In a coronation first, members of the public are invited to pay homage to Charles too, led by the archbishop.

The public homage sparked controversy when plans for it were first revealed, with critics saying they should not have to pledge allegiance to the king. The archbishop responded to the controversy by telling the BBC the oath is "an invitation; it's not a command.”
Charles' younger son Harry was seen in the congregation paying homage to his father.