I have never seen the Queen looking so happy. Smiling, beaming, laughing, she lit up a grey day at Balmoral as she arrived to take up residence at the castle for the first time without Prince Philip, her relaxed good humour obvious to spectators delighted to see her back at her Highland estate which has always meant so much to her as late summer becomes autumn.

Radiance is not the Queen’s default setting. And yet her delight at being on home ground, seeing again Corporal Cruachan 1V, the Shetland pony mascot of the Royal Regiment of Scotland, on his best behaviour for once, was palpable. It was a charming scene, the Queen wearing the regiment’s crest as a diamond broach on the shoulder of her pink coat. And yes, she was radiant.

I have written and filmed many reports about the Queen since I became a journalist 59 years ago but never have I witnessed the evident joy that she is taking now in every aspect of life, from meeting the G7 leaders in Cornwall at a glittering dinner that was a great example of exercising “soft power”, to once again returning to her beloved Scotland, her mother’s home country.

Don’t get me wrong. The Queen is never glum. She is not a negative person. If she has reason to be sad, she also has the training to disguise it. As Head of State, personifying the country, she cannot be downcast, because of the pall that would cast over those around her and the nation as a whole.

An optimistic outlook is part of the job requirement and fortunately it comes naturally to a woman who, at 95, has the experience to know that everything tends to come out alright in the end.

Fortunately for her and her subjects, she is not, I believe, burdened with an over-active imagination that perceives disaster in every shadow. She has the outlook of what she chiefly is -- The Squire of Sandringham, a sensible countrywoman who has seen it all, heard it all and persists in the belief that people are fundamentally decent and only need inspiring leadership to embrace better and more fulfilling lives.

She never went to school. When she joined the Brownies, the pack came to her. Her every waking moment has been closely observed. Almost all her activities are calculated and planned. And yet, a woman who is unique in so many ways seems to be endowed with common sense and the flawless ability to put everything into proper context.

Even the death of her husband after 73 years of marriage has been rationalised. No longer prey to poor health and declining powers, the Duke of Edinburgh was given the funeral he had planned; no nonsense. The weeping for a life that could hardly have been fuller was kept behind Castle walls. As Sophie, the Countess of Wessex, said at the time: “The Queen is amazing”.

Why is she so happy? I am sure it’s because she sees greatness in Prince William and the Duchess of Cambridge. If Hollywood were casting a young prince waiting to take the throne following a reign that has broken every record, it would come up with someone like Prince William: tall, good-looking, highly articulate, patently sincere and blessed with the good judgement that is only revealed when it is put to the test, as Prince William’s has been, not least in his handling of the Meghan and Harry saga.

That has had little or no impact on the Queen’s peace of mind, nor, I think, will the latest development in the sad story of Prince Andrew’s entanglement with the late Jeffrey Epstein.

Her lawyers will have advised the Queen that US law may be mighty, but its writ does not run in her realms. Prince Andrew is being sued not prosecuted. It’s a civil action, not a criminal one. Prince Andrew does not live in America and, as far as I know, owns no property there. As long as he does not go to America, he is safe.

In my opinion it is not a good look -- the Queen’s son unable to visit Britain’s most important ally without being slapped with a subpoena -- but the Prince’s lawyers will continue to play a dead bat to the accusations against him by Virginia Giuffre, who alleges she was abused by Andrew in 2001 when she was 17, although the Prince maintains he has never “met the lady”.

Next year’s celebrations of the Queen’s utterly unprecedented 70 years on the throne will not be dimmed by any of this. And judging by social media reaction, most people regard more whingeing from Prince Harry, as he enjoys enormous luxury in the California sunshine, as an unflattering look for a middle- aged man rich enough to run away and thus avoid the worst privations suffered by millions during the pandemic.

The Queen’s only concerns are what they have always been: how goes my realm and what about Succession?

There will always be problems, and Britain has had more than its share lately, what with the tortuous Brexit negotiations being immediately trumped by the pandemic.

As for the House of Windsor, it looks to be built on strong foundations, with Prince William as heir presumptive, his wife Kate the perfect future Queen who rarely puts an elegant foot wrong, and three beautiful children who are being brought up in a loving family, giving them every chance of becoming well-rounded people.

King Farouk, the overthrown last king of Egypt and great glutton and gambler, predicted that in 100 years there would be just five kings left: The kings of hearts, clubs, diamonds and spades -- and the King of England.

Who knows, even Australia, New Zealand and Canada may choose to think again about discarding the Monarch as Head of State when, here ready-made, there is a Commonwealth First Family as attractive as King William V and Queen Katherine will undoubtedly be.

Of course, Prince Charles will succeed his mother if she dies before him. But the Queen does not just look happy, she looks in robust good health. And her mother lived to be 101.

I remember stories published in 1985 that the Queen had an unspecified “heart condition”. The next day, the Queen went to Aberdeen and climbed the 90 steps to the top of a lighthouse, following that with a hike up the Great Wall of China the next year with her courtiers trailing behind.

In those days, courtiers said they could tell if the Queen was displeased about anything, she would wear what they called her “Piggy Face”. Miss Piggy hasn’t been seen for years. Perhaps she has been banished by Royal Decree.