Prince Philip gave words of comfort to Prince Charles after his divorce from Princess Diana.

The Prince and Princess of Wales had a fairytale-like wedding. Millions of people around the world witnessed it on national television and thousands gathered to see the couple exchanged “I dos.” However, it was not a secret that they had an unhappy marriage.

Prince Charles was already in his 30s when he got married. Although Princess Diana was considered the perfect bride for the future king, she was still too young for him. They had a miserable union to the point that Queen Elizabeth II ordered them to get a divorce to officially end their marriage.

According to royal biographer Angela Levin in her book “Harry: Conversations with the Prince,” the heir apparent was so upset because he felt that he let down his parents, grandmother and the public with his failed marriage. However, Prince Philip who was very critical with his son showed sympathy to him.

“Based at Highgrove, Charles was consumed with guilt that he had made Diana so unhappy and in doing so had also let down the Queen, the Queen Mother, Prince Philip, his sons and the British people,” Levin wrote.

“He found a rare moment of solace in a letter he received from his normally critical father wrote that he felt Charles had displayed he had the ‘fortitude of a saint’ by putting up with Diana.”

Many believed that it wasn’t Prince Charles’ fault alone that their marriage didn’t work because the late Princess of Wales had been difficult, too. However, royal fans still blamed the heir apparent because of his prolonged affair with Camilla Parker Bowles.

Meanwhile, in one of Prince Philip’s letter addressed to Princess Diana, he called his own son silly for leaving Prince William and Prince Harry’s mother for Camilla. The Duke of Edinburgh wrote that he would do his best to help the Prince and Princess of Wales keep their marriage and the future king was “silly” to risk everything for Camilla because they never thought Prince Charles would feel like leaving his first wife.

Prince Philip and Prince Charles Prince Philip made Prince Charles nervous and neurotic after sending him to Gordonstoun. Pictured: Prince Philip and Prince Charles n to speeches before a statue of the Queen Elizabeth, The Queen Mother was unveiled on Oct. 27, 2016 in Poundbury, England. Photo: Getty Images/Justin Tallis