She is said to have exchanged a few words with Prince William at Westminster Abbey

The Coronation of King Charles was one of the most important events on the Royal calendar last year. It required months of planning, with all members of the Royal Family prepped on the special occasion.

Both Prince William and Catherine, Princess of Wales played key roles during the celebration – and they were keen for it to go ahead without any hitches. According to a lip reader, Kate Middleton issued a concerned four-word warning to her husband ahead of his father’s Coronation.

Eager to avoid any slip-ups, she made her remark to Prince William as they arrived at Westminster Abbey. They then joined the procession before the crowning.

Both wore formal robes with Kate donning a striking Royal Victorian Order mantle. Prince William wore his Order of the Garter mantle, MirrorOnline reports.

The couple lined up as they waited for the procession to begin. They were captured by cameras as they exchanged words with each other.

It appeared that the princess had a few concerned words to share with Prince William. Professional lip reader Jeremy Freeman told the Daily Star that Kate turned to William and said “just mind the gown”.

He believes the heir to the throne replied with reassurance, telling Kate “don’t worry I got [or caught] it.” But it seems they had no reason to worry as the ceremony went ahead with no issues.

But there was one mysterious detail on Kate’s outfit which sent royal fans into a frenzy. When the official Coronation photos were released, her robe largely covered her Alexander McQueen dress but she had ditched the mantle.

Fans noticed that the V-shaped neckline of the dress in the official photo was different to when she was at the Abbey. It led to speculation online that the princess may have had two dresses made – despite the embroidery on the skirt remaining the same.

But the mystery of the dress’ neckline now appears to have been explained – and it seems it could have all been down to a separate garment. According to Alastair Bruce, Sky News commentator and royal expert, Kate wore an additional cape over the top of the dress in order to protect it from the heavy mantle and chains she was required to wear over the top.

It then appears she removed the cape for the official Coronation photos. It revealed the intricate V-shaped neckline, which showed off the George VI Festoon necklace – a gift to the late Queen Elizabeth in 1950.

The McQueen dress was created from ivory silk crepe with silver bullion and threadwork embroidery featuring rose, thistle, daffodil and shamrock motifs, representing the four nations. Her look was completed with a Jess Collett x Alexander McQueen headpiece with silver bullion, crystal and silver threadwork three-dimensional leaf embroidery.