“And within hours of that happening that was leaked from the Sussex side to favoured media and that really crossed the line in the sand for the Royal Family because so very little of their lives is genuinely private. So much is lived in public or even surrounded by staff watching everything they do. So private conversations, particularly private phone calls are really considered just that.”

And t here is currently one sign that shows that father and son are unlikely to meet despite both being in the UK – and it is down to the King’s schedule. Just days before the WellChild Awards on September 28, Charles and Queen Camilla will attend the Scottish Parliament in Edinburgh to mark its 25th anniversary.

According to The Telegraph, the King is likely to spend the days after the engagement north of the border in Scotland. Harry’s event is in London, meaning they will be hundreds of miles apart – although there is still time for plans to be made to faciliate a meeting between the pair.

Harry was last in the UK several weeks ago to attend the funeral of his late uncle Lord Robert Fellowes, the husband of Princess Diana’s sister Lady Jane Fellowes. On that occasion, he did not meet up with his dad, although the event was also attended by Prince William – but the two warring brothers are said not to have spoken to each other.

Before that, Harry was in the UK in May for a 10th-anniversary service for the Invictus Games at St Paul’s Cathedral in London, with the King also in the capital on the same day. It had been hoped that father and son were on the road to begin repairing their rift, especially after they met when Harry dashed to the UK after it was announced that Charles had been diagnosed with cancer in February.

However, eyebrows were raised at the time, with a statement from Harry suggesting his father was too busy to see him and reports later claiming the King had offered his son a place to stay in a royal residence.