Originally Published: 11 JUN 21 12:14 ET

Analysis by Max Foster and Lauren Said-Moorhouse, CNN

(CNN) -- A version of this story appeared in the June 11 edition of CNN's Royal News, a weekly dispatch bringing you the inside track on the royal family, what they are up to in public and what's happening behind palace walls. Sign up here.

London (CNN) -- Joe Biden is in for quite a treat when he and his wife, "Jill from Philly," stop by Windsor Castle this Sunday. To welcome the 46th President, Elizabeth is treating him to an honor guard formed of the Grenadier Guards in the castle's famous quad, Buckingham Palace has announced. The guards -- one of the British Army's longest-serving units -- will give a Royal Salute, and the US National Anthem will be played.

The Queen has hosted four other presidents at Windsor: Trump in 2018; Obama in 2016; George W. Bush in 2008; and Reagan back in 1982.

The President will then inspect the troops before rejoining the Queen and first lady to watch the military march-past. Afterward, the group will head into the castle for tea. During our chat with Prince Edward, he discussed the opportunity Biden has in meeting his mother and how others have reacted to spending time with her.

"When you meet somebody who's had that level of personal experience and knowledge, it's, I mean, sometimes, it's funny and can slightly over-awe some people," the 57-year-old mused. "And I think most people can leave wishing that they'd had a little bit longer. That's usually the response -- just so would've liked to have had a little bit longer, because that was fascinating."

Ahead of the weekend's big meeting, the royals are undertaking something of a charm offensive at the G7 in Cornwall. The Queen, Prince Charles and Camilla, as well as William and Catherine, will descend upon the summit for a reception at the world-famous Eden Project, a striking collection of biomes, one of which is home to the largest indoor rainforest on Earth.

Kate met the first lady earlier on Friday. The duchess has long championed early childhood education. The pair participated in a roundtable discussion on the subject and toured a school in Cornwall.

THE RULES BIDEN SHOULD FOLLOW WHEN HE MEETS THE QUEEN

A meeting with the monarch can be intimidating ... even if you are a world leader. The Queen has met nearly every US President to take office during her lengthy reign.

No doubt keen to make a good impression on his first trip abroad, Biden will probably want to follow the established conventions for his one-on-one with the 95-year-old monarch. Here's a quick rundown of the royal rules of engagement.

What you should do

-There is no obligatory code of conduct to abide by when greeting royals, according to the family's website. However, it does acknowledge that some may choose to observe "traditional forms."

-Basically, that means the Queen doesn't expect people to bow to her, though many do so anyway. For men, that could be a gentle dip of the head, while women can opt for a small curtsy. You could also add a handshake (if she offers first!) but, either way, the secret is not to overdo it.

-When meeting the Queen, tradition dictates that she speaks first. In response, the correct form is to first address her as "Your Majesty" before swapping to "Ma'am." And in case you were wondering, there is a preference in pronunciation here -- it should be "Ma'am" to rhyme with "jam." Whatever you do, don't use her first name.

-Although royal protocols have relaxed in more recent years, a top tip is to take your cue from the Queen. If she walks, you follow; if she sits, you can too; and if dinner's involved, best wait for her to start before tucking in. We all remember Donald Trump's gaffe when he blocked the Queen and then walked ahead of her during his visit to Windsor.

What you should avoid

-Don't be late. According to Debrett's, the leading authority on British etiquette, "It is correct for everyone to arrive before the royal personage and protocol rules that no guest should leave an event before a member of the Royal Family, except in special circumstances when prior permission should be obtained." If you do need to duck out, make sure to seek permission through a private secretary first.

-It may seem obvious but don't touch the Queen without her consent. She initiates any contact -- and that's a handshake at most. In 2017, the then-Canadian Governor General David Johnston made headlines when he placed his hand on the Queen's elbow during a visit to Canada House in London. Johnston later said he was simply "anxious" about slippery carpet and chose to forgo convention "to be sure that there was no stumble."

-And probably best to avoid going in for a hug. It was quite a frenzy in 2009 when then-first lady Michelle Obama instinctively embraced the Queen (who sort of reciprocated). The British media had a field day, with conflicting observations about the moment. That said, Obama recalled a subsequent visit to Windsor Castle in 2016, when she was fretting over royal protocol but the monarch shrugged it off, declaring it "all rubbish."

Other things to keep in mind

-You can bring a gift but make sure it's appropriate for the occasion. Official gifts go into the Royal Collection -- one of the largest private art collections in the world -- even if they are given to a specific family member.

-So, what do you get the monarch who has everything? Well, it's tricky. Trump went with a Tiffany & Co. silver and silk poppy brooch in a custom White House wooden jewelry box in a red leather case when he returned to the UK for a state visit in 2019. His predecessor went in a different direction, with Obama presenting the Queen with an iPod pre-loaded with Broadway songs and video footage of her 2007 trip to the US.

Confused? Ok, then here's the one hard and fast rule to cling to: If in doubt, leave it out. The last thing you want to do is attempt to follow the nuanced and often unspoken royal rules only to fall foul. At the end of the day, the United States is not a realm or territory of the Queen. Following protocol is polite but not the law. The President won't be barred from ever returning if he slips up. Ultimately, it's Biden's call what he does or doesn't do -- even if we'll all be watching.

QUEEN'S YOUNGEST STEPS INTO SPOTLIGHT

Harry and Meghan's departure from official royal duties has left a void in the British monarchy. It hasn't just lost the charisma and precious diversity that came with the couple, the institution also lost key senior people to do the work. Family members carry out hundreds of engagements a year on behalf of the Queen and someone else must now pick up the slack.

The Earl and Countess of Wessex -- Prince Edward and Sophie -- have always carried out their fair share of duties, but they have taken more high-profile roles as royal ranks have slimmed. That may help explain why Edward agreed to a sit-down interview with CNN. He was keen to take stock of his father's legacy ahead of what would have been Prince Philip's 100th birthday, in particular the Duke of Edinburgh's Award program, which gets young people out of the classroom and building confidence in the outdoors.

Unlike those higher up the line of succession, Edward isn't surrounded by courtiers. We brought up the family rift, which, let's face it, could have been awkward, but instead Edward defused the situation by tackling it head on with a grin: "Are you euphemistically referring to Harry and Meghan?" ... to which we answered: "Yeah, er, yes."

While he laughed at the delicate phrasing of our question, his seriousness returned while recognizing the Sussexes' decision to step back was not an easy one for the pair to make -- and that was important.

The public reaction to Harry and Meghan's admissions that their mental health suffered during their time as working royals has been mixed. For some, it was too personal, especially when the royal mantra has always been "never complain, never explain."

But for many, the Sussexes' remarks were relatable and reflective of how society is shifting. To them, the lack of public response from the family to address the couple's experiences thus far was disappointing. And the social media reaction shows that some appreciated Edward's choice to be just a little more open and transparent, despite the unofficial palace strategy to retain a "dignified silence" in the face of the many revelations and claims coming from the Sussexes in recent months.

Catherine Haddon, a constitutional expert at the think tank Institute for Government, recently spoke with CNN about how leaning on royal convention doesn't always work nowadays. She said: "With increasing loss of deference in society and increasing pressure for greater transparency, it is hard for the monarchy to stick to the old ways of doing things."

Edward, for his part, spoke of public perception when recalling his father's legacy, reminding us there is no handbook to being a royal. "You have no idea whether or not you're doing it right or wrong," the earl told us. "You just hope to goodness it's the right thing, unless somebody comes out and tells you, really."

To some, that may seem like a cop out. But the reality is that people working around royals are instinctively reverential. It would be wrong to describe them as yes-men and yes-women, but they know who's boss -- and that the boss is never going anywhere. That leaves a small circle of family and trusted confidants to call royals out when they do get it wrong.

Any monarchy is a living institution that must develop to survive. The British one is being forced through a particularly rapid evolution. The Wessexes are now likely to become household names globally. With this interview, Edward proved he was not out his depth -- in fact, he was a breath of fresh air. Next job: retain the family's relevance and restore public opinion that may have been recently diminished.

WHAT ELSE IS HAPPENING

How the Queen is celebrating her official birthday this year

For the second year in a row, Elizabeth's annual summer birthday celebration has been curtailed by the pandemic. In normal times, the royal family enjoys the famous Trooping the Colour event, which has marked the British sovereign's official birthday for more than 260 years. Once again, it will be moved from central London to the confines of Windsor to prevent well-wishers from congregating. Accompanying the Queen in the quadrangle will be her 85-year-old cousin, the Duke of Kent. The royals will view a military parade led by the Foot Guards, as well as The King's Troop Royal Horse Artillery and the Household Cavalry Mounted Regiment. A 41-gun royal salute will also be fired from the East Lawn of the castle.

Remembering grandpa

Several royals took to social media on what would have been Prince Philip's 100th birthday. Princess Eugenie posted a photo of her grandparents on Instagram, saying she was "thinking of Grandpa." The Prince of Wales and Camilla uploaded a series of snaps, including a heartwarming black and white photo of a young Charles holding his father's hand after the duke returned from a trip to Malta. Meanwhile, the Queen was gifted a rose named in memory of the Duke of Edinburgh by the Royal Horticultural Society last week. The newly bred deep-pink rose has since been planted in the East Terrace Garden at Windsor Castle, which Philip had a hand in designing.

Harry sends condolences after mine clearance workers shot to death

The Duke of Sussex has interrupted his parental leave to issue a statement condemning an attack on staff from international demining charity the HALO Trust earlier this week. An ISIS affiliate in Afghanistan, known as IS-K, claimed responsibility for Tuesday's attack, which killed 10 and injured 16 others, according to the SITE Intelligence Group. Harry called the attack "nothing less than an act of barbarism." He added: "These workers put their lives on the line every day to make the world a safer place. This brutal act reminds us that we must stand in solidarity with humanitarian aid workers and the communities they serve." The duke has had a long-standing link with the organization. In 2019, he poignantly revisited an Angolan minefield that his mother, Diana, had traveled to months before her death in 1997.

Charles' joy over baby Lilibet

Prince Charles declared the arrival of his fifth grandchild, Lilibet, "such happy news." He made reference to the littlest royal while speaking about innovation and the need to maintain the world for future generations during a visit to the BMW Mini car factory in Oxford, England. You can watch the moment here. On Wednesday, Harry and Meghan denied a report in the British media that they didn't ask the Queen about naming their daughter after the monarch's childhood nickname. A spokesperson for the Duke of Sussex told CNN that Harry spoke with the Queen before the announcement, and said she was supportive of the decision. The birth was announced Sunday. Baby Lili is a sister for the couple's 2-year-old son, Archie Harrison.

PHOTO OF THE WEEK

FROM THE ROYAL VAULT

In honor of the monarch's official birthday this weekend, CNN Style is taking a closer look at our fabulously colorful Queen. In her 69 years on the throne, she has become renowned for her love of vivid hues and pops of pattern. But there's a lot of strategy behind Elizabeth's color block couture.

Undoubtedly, her sartorial choices are an expression of her identity. But she also needs to stand out so that the crowds who have gathered to see her can actually spot her. And when she's among other royals, her bold colors often make her stand out from the rest of the family. "I can never wear beige because nobody will know who I am," the Queen reportedly once said.

What the Queen wears matters and must be appropriate. She has, over the years, masterfully used color palettes and symbols to honor nations. For example, for her historic state visit to the Republic of Ireland in 2011 -- when she was the first British monarch to visit in a century -- careful consideration was demonstrated in her wardrobe. She wore Ireland's de facto national color of green and, later in the trip, a silk gown embellished with more than 2,000 hand-sewn embroidered shamrocks and an Irish harp brooch made from Swarovski crystals.

Angela Kelly, who has been dressing the Queen since 1994, says the sovereign is thrifty, outfits can be worn multiple times and last for decades. Read the full story here.