Prince Charles and Princess Diana
Prince Charles showed signs of distress during his wedding to Princess Diana. Pictured: Prince Charles and Princess Diana at their wedding at St Paul Cathedral in London on July 29, 1981. Getty Images/STR

Prince Charles may have hinted that his relationship with Princess Diana was on the rocks as early as his wedding, says one expert.

On Saturday, another royal wedding will happen as Prince Harry and Meghan Markle tie the knot. While many experts agree that the couple appears to be compatible and very much in love with each other, this was apparently not the case for Prince Charles and Princess Diana.

According to body language expert Dr. Peter Collett, the Prince of Wales was already showing signs of his rocky relationship with the late Princess of Wales even before their big day. His behavior apparently revealed his discomfort.

"When Prince Charles and Diana announced their engagement there were already signs that all was not well," Collett said (via Express). "We can see that they together, but they are not in step and Charles is not adapting his behaviour to include Diana."

"In fact, if we apply the cut-out principle, and remove Diana from the scene, it does not look like anyone is missing," the expert continued.

The doctor added that Prince Charles showed more signs of distress before their wedding ceremony. When they were asked if they were in love, the Duke of Cornwall reportedly "offered his famous evasive answer."

"Whatever love means, it's your own interpretation," Prince Charles said.

"When the interviewer provides a standard definition we notice Charles looking down and biting his lip, indicating he has realised he has just said the wrong thing," Dr. Collette explained.

Aside from showing signs of distress, Prince Charles' actions apparently also revealed that he was unhappy.

"At a crucial point he wipes away his imaginary tears. This is an action that people often perform when they are feeling sad," the expert added. "It suggests that Charles is having deep regrets about what he has got himself into."

Meanwhile, things were different when it came to Camilla Parker-Bowles. During Prince Charles' wedding to Camilla, there were fewer signs of distress.

In related news, another body language expert, Judi James, claimed that Prince Charles has changed and learned to mirror his second wife. Mirroring is an indication of comfort, trust and rapport between two individuals.

"Camilla's body language is identical to when she was first dating Charles and this resilience and lack of change must be hugely attractive to a man who lives in what might be a very chaotic world," James told Express.

"She has the same wide grin, head-tilt and hair-raking gesture as she sports in their photos years before and the effect on Charles has been dramatic," the expert continued. "He is now mirroring his wife with a mirrored wide grin that covers his entire face. Charles is the one who has changed dramatically to mirror his wife."