Prince William reveals King Charles suffering secret pain from wearing Coronation crown

King Charles III was left with a sore neck and head last night after his Coronation, his son Prince William has explained.

Heavy is the head which wears the crown, they say - and that was the case for Charles who was left aching from having the five pound crown on for hours.

Speaking to fans outside Windsor, the Prince of Wales today revealed: "I think his neck hurt last night, having the crown…it does weigh a hell of a lot."

Our newest monarch wore the 17th century St Edward's Crown during the ceremony at Westminster Abbey yesterday as more than 2,000 guests watched on.

Charles and Camilla wore lighter crowns after the ceremony (AP)

Due to the sheer weight of the crown, most royals will swap the heavy crown for the much lighter Imperial Crown. This is exactly what Charles did on his way out, but he was still left with some aches and pains.

While talking to fans outside on today's walkabout, William apologised for those who had to endure the rain yesterday.

"I felt so bad for everyone yesterday standing out for hours in the rain," he said.

"We’re so British…everyone gets this. ‘Yeah, Yeah, bit of rain, we’ll manage."

The King was left sore after wearing a heavy crown during his Coronation (Getty Images)

The future King also said how nervous his father was for the historic event.

When asked about any nerves King Charles had, he replied: "Yeah, I think so. It's always one of those days when everyone is watching and you want it to go all smoothly and well."

Camilla chose a refreshed version of Queen Mary's crown, containing stones and designs that pay tribute to Queen Elizabeth II.

The royals on the Buckingham Palace balcony (POOL/AFP via Getty Images)

The crown has four arches and a 18.8 carat heart-shaped stone, from Cullinan V diamonds, and above the stone there is a 94.4 carat pear-shaped Cullinan III Diamond.

Below the heart-shape is a 63.6 carat cushion-shaped Cullinan IV Diamond.

Both the Cullinan III and Cullinan IV diamonds were part of Queen Mary's original crown, created in 1911 for Queen Mary, the consort of King George V.

Prince William spoke to the crowd outside Windsor (PA)

During the crowning, Charles was also presented with an orb, a sword and a sceptre and had the solid gold, bejewelled St. Edward’s Crown placed atop his head as he sat upon the 700-year-old oak Coronation Chair.

Following the ceremony, he stepped into a gilded horse-drawn carriage with his queen and rode off to his palace.