He wrote in the Daily Mail: "All the mutual friends I have encountered find themselves seeing both points of view — William's defensiveness of the monarchy as he sees it, and Harry's defensiveness of his wife.
"Love versus duty. This is what makes it so painful. The friends commiserate with each other over the tragedy they are witnessing, and they frequently discuss how to heal the breach — though with an increasing sense of despair.
"Sussex supporters have noted the bizarre combination of self-promotion and self-pity that seems to characterise Meghan, and can see why it has infuriated William.
"'Meghan can be a 500 percent nightmare,' some close friends of Harry are among the first to admit. 'The never-ending PR. She's just so . . . American!'
"On the opposite side, friends of William and Kate are willing to concede the jealousy the Cambridges once felt at being overshadowed by the megawatt younger brother and his wife."
Mr Lacey added Harry may also be hoping to reconcile with William and old friends, but they may not be so forgiving.
He wrote: "I'm told that Harry has been telling friends he would like to reconcile, and is willing to admit some of the missteps he has made.
It comes as Harry is set to reunite with William as he is now back in the UK for the unveiling of a statue of his late mother Princess Diana, on what could have been her 60th birthday.
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3.10pm update: Prince Harry used HRH title he gave up on Lilibet Diana's birth certificate
Prince Harry flew into the UK and fresh controversy yesterday ahead of joining brother Prince William at the unveiling of a statue of Princess Diana.
James Bickerton takes over reporting from Rachel Russell
2.29pm update: Charles 'seemed to be taking different path to Harry' in echoes of claim about William
Harry is currently quarantining in the UK after arriving in London during the week. He has returned to accompany William at an unveiling of a statue of their late mother Princess Diana in the grounds of Kensington Palace next week.
Royal watchers the world over are eagerly anticipating the event given the current set of circumstances surrounding Harry and the rest of the Royal Family.
While the Duke of Sussex only recently visited Britain in April to attend Prince Philip's funeral, he has since appeared in broadcast interviews speaking out against The Firm.
The bad blood stems from Megxit and his and Meghan Markle's epic fall out from royal life last year.
One of the biggest indicators that something was wrong came when Harry spoke in an ITV documentary during his and Meghan's tour of southern Africa.
Here, Harry addressed some reports in the media that he and William had not been getting along, and said: "We're brothers, we'll always be brothers.
The differences in handling Meghan's treatment was explored in Channel 5's documentary, 'William & Harry: Princes At War?'.
The show's narrator noted: "The Royal Family may have been reassuring Meghan behind the scenes, but it's their standard practice not to complain in public about press treatment.
"By apparently not speaking up for Meghan, Charles seemed to find himself taking a very different path to Harry."
1.50pm update: Meghan and Harry's Netflix hopes crushed after US rejection: 'No one wants to watch!'
Harry is currently self-isolating after arriving in the UK from the US. Next week, he will meet with his brother Prince William to unveil a statue of the pair's late mother, Princess Diana. It is the first time the Duke of Sussex has visited his family since Prince Philip's funeral and appearing in a string of broadcast interviews in which he spoke out against The Firm.
The Queen was seen driving on Friday evening in Windsor just hours after Harry's arrival.
He is staying at Frogmore Cottage, and according to The Sun, Her Majesty was driving towards the royal residence.
Harry was largely absent from royal life when he and Meghan Markle departed the UK for North America last year.
Ties were further severed when the pair announced they would no longer be rerunning as working royals earlier this year.
Carving out new, private lives for themselves, Meghan and Harry have taken on a range of responsibilities including securing lucrative job contracts.
Netflix offered them a sum thought to be worth ￡109million to produce original content.
The pair have yet to create anything but announced in April that they had started work on a series about the Invictus Games as competitors prepare for the 2022 event.
While many have welcomed the possibilities of their creations, others have outright rejected them.
12.59pm update: Queen took Sophie Wessex ‘under her wing’ when Countess was rushed to hospital
According to royal experts, Sophie, Countess of Wessex, nearly died when her daughter was born a month early. In 2003, the Countess had a sudden placental abruption, where the placenta prematurely separates from the uterus.
She had to have an emergency caesarean and her daughter Lady Louise Windsor was born November 8, 2003.
According to royal author Ingrid Seward, the Queen and Sophie’s bond became strong during this traumatic birth experience.
She told the Times: “[Sophie] nearly died. The Queen went to see her in hospital, which was unheard of.
“She rather took Sophie under her wing, maybe from that moment on.”
11.57am update: Meghan Markle called ‘merciless’ by Prince William - bitter row with Harry continues
William is believed to still hold "anger" over allegations Meghan bullied royal household staff members, which she has denied.
Mr Lacey said: "Some inching towards reconciliation seemed in progress, their watching friends dared to dream — as did the whole world.
"But those hopes were dashed within minutes of the siblings getting inside the castle and beyond camera vision. They started quarrelling again.
"There they were, at each other's throats as fiercely as ever,' relates one long-time friend with a tired and helpless shrug.
"The rage and anger between those two has grown so incredibly deep. Too many harsh and wounding things have been said.
"So there's the bad news. The conflict between Diana's two bitterly divided sons does not seem likely to end any time soon.
"According to one of my sources, it's been pointed to him that everyone has a difficult sister-in-law.
"William's response was to nod his head in sage acceptance. Then suddenly he broke out angrily. 'But look at the way that bloody woman treated my staff — merciless!'
11.15am update: Kate CUT from Princess Diana statue unveiling-William and Harry representing royals alone
A royal source told the Mirror: "The Duchess has seen this project evolve from its conception and now to the finished article and undoubtedly wants to be there to support her husband.
"No doubt there will be tensions between the Cambridges and Harry, but they all recognise that despite the obvious and deep-rooted issues between them, they want the day to be solely about the Princess of Wales’s enduring legacy."
Kate has been described as the family’s “peacemaker” by her uncle Gary Goldsmith.
He told Closer: “If anyone can bring peace to the royals, Kate can. Kate is a brilliant arbiter and peacemaker.
“Every bone in her body is about making friends and doing the best she can… she’s trying to mediate.”
10.10am update: Charles honours armed services
The official Clarence House Twitter page posted: "On #ArmedForcesDay, we honour the incredible work and dedication of the men and women in the Armed Services community – from currently serving troops to Service families, veterans and cadets.
"Since the start of the pandemic, our Armed Forces have been there to help the nation through the difficult times, from setting up Covid-19 testing sites to supporting the NHS by assisting ambulance workers.
"Thank you all for your service."
9.02am update: Princess Beatrice's husband Edo pens heartbreaking message about couple's unborn child
Edoardo Mapelli Mozzi took to Instagram to mark the 10th anniversary of Christopher Shale's death. The millionaire property tycoon said he wished his step-father had got to meet his grandchildren, including his and Beatrice's impending arrival.
Beatrice's husband shared a series of snaps of his step-father in the touching Instagram post.
In the caption, Edo said: "Chrisdog, Pups, I can’t believe it has been 10 years.
"Not a day goes by without me thinking of you and leaning on all the lessons you taught me.
"You once said on my 18th birthday that being my stepfather was the greatest honour and privilege of your life.
"I echo this, being your stepson is the greatest honour of my life and I would never be standing here today without you.
"I know how proud you would be of us all today and so wish you had got to meet your 3 and soon to be 4 grandchildren.
"What joy they would have brought you.
"I was just Wolfie’s age when you came into my world and changed everything.
"You always believed in me, with unconditional love.
"You taught me honestly, laughter, hard work and empathy.
"I love you today and always."
8.26am update: Prince William may be first to abdicate in decades amid royal shake-up after Queen's reign
Prince William could become the first British royal of this century to abdicate, royal expert Ian Lloyd said. The expert believes the end of the Queen's reign will bring upon many changes to the Firm.
One of them, Mr Lloyd said, could be a different approach to service as a monarch.
Rather than serve as monarchs for their whole lives, the future generations of British Kings and Queens may follow the examples set in European monarchies and retire when they reach an age that could prevent them from fully carrying out their duties, the author explained.
Mr Lloyd, however, believes a similar change could be seen from Prince William's reign, as Prince Charles will likely "want to have a bit of time as King".
The author of 'The Duke: 100 Chapters in the Life of Prince Philip' told Express.co.uk: "Most of the other monarchies in Europe have abdications - for example King Juan Carlos of Spain, Queen Beatrix of The Netherlands and Albert II, the King of Belgium retired.
"The abdication and retirement of monarchs are commonplace in Europe."
8.03am update: Queen will not 'share her feelings' over the 'behaviour of Meghan Markle and Prince Harry'
An official Buckingham Palace said after Harry and Meghan's Oprah interview was aired that "recollections may vary", but the Queen has not personally made a comment about it.
Similarly, her official team congratulated the couple on the birth of daughter Lilibet earlier this month, but it is not known what the Queen thinks about her nickname being used.
Royal expert Ingrid Seward claimed Her Majesty would not break away from the royal tradition of staying neutral to "reveal her feelings".
She told Express.co.uk: "I think the Queen will remain impassive about both the behaviour of the Sussexes and the naming of their baby girl Lilibet.
"Whatever she may think privately she will not reveal her feelings.
"It is personal and I feel certain she will keep it that way whatever they do."
7.54am update: Princess Anne followed father Philip's lead with reaction to 'Harry and Meghan drama'
Harry was briefly reunited with the royals earlier this year when he flew from his US home for Philip's funeral in April - just weeks after the interview was aired.
He was pictured speaking to brother William and sister-in-law Kate, but it is not known if he spoke to Anne as they kept apart during the service..
Royal expert Ingrid Seward said Anne is likely to have chosen to not "get involved" in any of the issues surrounding Harry when he returned.
She added Anne will have probably chosen to follow Philip's trait of "distancing himself from issues he didn’t consider his business".
She told Express.co.uk: "Anne has no need to get involved in the Harry and Meghan drama at all.
"Remember she is her father’s daughter and he frequently choose to distance himself from issues he didn’t consider his business."