Amid all the splendour and pageantry of a state visit this week, King Charles and Japan‘s Emperor Naruhito will reignite a friendship forged over fly-fishing and barbecues at Balmoral.

It will be a chance to catch up and help promote the relationship between their two modern countries and perhaps compare notes on how their two ancient but ‘slimmed-down’ monarchies operate in the 21st century.

The two men bonded back in 1984 when Naruhito, the grandson of the then Emperor Hirohito, was a student at Oxford and spent a few days at the Royal Family‘s Highland retreat.

‘The Queen drove me around and invited me to a barbecue at a building in the grounds and Prince Philip personally guided me around the grounds in a horse-drawn carriage,’ Naruhito said last week. ‘These remain very cherished and nostalgic memories for me.’

Naruhito, 64, and Empress Masako, 60, have been staying at Claridge’s in Mayfair after arriving on Saturday. The official visit begins from lunchtime today and lasts until Thursday morning.

The couple will receive all the normal fanfare of a state visit – a ceremonial welcome at Horse Guards, lunch and a glittering state banquet at Buckingham Palace, and a trip to Westminster Abbey to lay a wreath at the grave of the Unknown Warrior.

But although Rishi Sunak and Sir Keir Starmer will attend the state banquet, there will be no traditional visit to Downing Street or Parliament for the imperial couple because of the election campaign.

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Emperor Naruhito and Empress Masako of Japan arrive for a state visit to the United Kingdom at Stansted Airport on June 22, 2024

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Prince Naruhito, Princess of Wales, Princess Diana and Prince of Wales, Prince Charles are seen at the Shugakuin Imperial Villa on May 9, 1986 in Kyoto

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Prince Charles And Crown Prince Naruhito Of Japan attending The Japanese Exhibition Matsuri Japan in Hyde Park. They are laughing while watching traditional Japanese dancing.

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The menu for the state banquet on Tuesday evening. Guests were served delicacies including poached Scottish langoustines, Cornish turbot and quail eggs

At a news conference last week, Naruhito also recalled Charles teaching him to fly-fish in the River Dee beside Balmoral Castle.

‘The [then] Prince of Wales carefully taught me how to put on a hair hook and how to throw it,’ he said.

‘We both put on waders and went into the river, where we saw big fish jumping nearby, but neither of us caught anything.’

He described how Queen Elizabeth invited him to tea at Buckingham Palace two days after he arrived in the UK as a postgraduate student at Merton College, Oxford, in 1983.

‘In a relaxed atmosphere, the Queen herself poured the tea, and we enjoyed a pleasant time together,’ he said.

‘I remember that the Queen shared stories about her visit to Japan and inquired about my upcoming life in the UK.’

Naruhito – who became Emperor in May 2019 after his father Akihito abdicated at the age of 85 arguing declining health meant he could no longer fulfil his duties – has met Charles and other members of the family several times since.

He has never forgotten the welcome he was given, particularly during that stay at Balmoral.

‘I fondly recall the heartwarming hospitality I received from the Queen and other members of the British Royal Family, who treated me as if I were part of their family,’ he said.

The 126th monarch to occupy the Chrysanthemum Throne – the world’s oldest continuous hereditary monarchy – and his Empress (who also studied at Oxford) will be reliving some of the happiest days of their lives during their stay in Britain.

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Naruhito was a student at Oxford between 1983 and 1986. Above: Naruhito in Oxford next to his bicycle, 1985

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The Duke of Edinburgh took Naruhito around Balmoral in January 1985 for what was in effect a tutorial in ecology and his first experience of British wild life

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Prince Charles fishing on the River Dee, in Ballater, near Balmoral Estate, on May 3, 1992

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King Charles, then the Prince of Wales, arrives for Emperor Naruhito’s enthronement ceremony at the Imperial Palace in Tokyo, October 2019

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Emperor Naruhito and Empress Masako attend the ‘Kyoen-no-Gi’ banquet celebrating their enthronement at the Imperial Palace

Other parts of the programme outside the official state visit include the Emperor going to Kew Gardens on Thursday, when he will also make a private visit to St George’s Chapel, Windsor, to lay a wreath at the tomb of Elizabeth II.

He and his wife will also see a Japanese exhibition at the Young V&A museum in London’s East End on the same day.

On Friday, their last day in the UK, they will return to their old colleges at Oxford.

Between 1983 and 1986 Naruhito studied 18th century commerce on the River Thames as a postgraduate.

Empress Masako, by then a young diplomat, studied international relations at Balliol College between 1988 and 1990.

He and Masako, who met in 1986, both did a bit of rowing and played other sports while at Oxford and developed a love of the historic city – particularly Christ Church Meadow – and the Cotswolds while there.

But for unexplained reasons, Masako did not complete her thesis before returning to Japan and it has not been plain sailing for her or the imperial family since.

She and Naruhito have a daughter, Princess Aiko, 22, but under Japanese law women cannot inherit the throne and the pressure to produce a male heir has been blamed for a stress-related illness that has led to her periodic absences – once for 11 years – from public life.

Her doctors have said she is not fully recovered and Masako, like Queen Camilla, still struggles at times with foreign travel.

She will be pacing herself on this trip, sitting out many of her husband’s engagements.

Japan’s monarchy, like Britain’s, has faced turmoil in recent years and is grappling with running as a slimmed-down entity.

The immediate succession crisis was resolved in 2006 when the Emperor’s younger brother and heir, Fumihito, now 58, had a son, Hisahito, in 2006.

But there is still a shortage of males and the women in the family lose their royal status when they marry commoners.

In 2021, Fumihito’s daughter Mako became the latest in a succession of princesses to lose her title when she wed a commoner.

It has led to a shortage of working royals in Japan.

Craig Prescott, a constitutional expert at Royal Holloway, University of London, believes there is much for both monarchs to compare and contrast this week.

‘I think they are both grappling with, in a sense, the weight of history,’ he said.

‘I think there is a lesson for the British monarchy about being too small a royal family,’ he added, pointing to the sharp drop in official UK royal engagements since the deaths of Queen Elizabeth and Prince Philip and the departures of Harry and Meghan and Andrew as working royals.

And this year of course has seen both the King and the Princess of Wales take time out to undergo cancer treatment.

Other working royals such as the Duke of Kent, Duke and Duchess of Gloucester, and Princess Alexandra, are well past official retirement age.

‘We have this 10-year gap before George, Charlotte, and Louis come on stream,’ Dr Prescott said.

Dr Prescott, who is writing a book on modern monarchy, agreed that King Charles was unlikely to call up younger relatives such as Princess Beatrice, Princess Eugenie, Lady Louise Mountbatten-Windsor and others to be official taxpayer-funded working royals to fill the gap.

But we might see more examples of them attending palace garden parties and other events and promoting their own charities to bolster the numbers and royal presence at times, he believes.

A joke for every banquet: King Charles’ witty cultural references

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Prince Naruhito poses for photographs on October 30, 1985 in Oxford

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Crown Prince Naruhito chats with friend Keith George at Merton College, Oxford, December 1983

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Prince Naruhito is seen while studying at Merton College of the Oxford University circa March 1985

Prince Naruhito plays the violin with fellow students at Oxford, February 22, 1984

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Prince Charles and Camilla stand between the then Crown Prince Naruhito and Crown Princess Masako in Tokyo, 2008

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Japan’s Emperor Naruhito views the coffin of Queen Elizabeth II inside Westminster Hall, 2022

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Emperor Naruhito and Empress Masako walking into Westminster Abbey on the day of the Queen’s state funeral

Britain changed its antiquated succession laws in 2013 to ensure that girls from then on enjoyed the same rights as boys, instead of older daughters such as Princess Anne having to sit behind their younger brothers in the line to the throne.

But Japanese conservatives are still opposed to women inheriting the throne.

Dr Prescott believes there will have to be consensus in public opinion before the monarchy in Japan can move on.

‘It’s a question that is about Japanese society as a whole,’ he said.

Where he thinks the British might eventually want to learn from Japan is the idea that a monarch can abdicate if they are too old or infirm to perform their duties.

It was anathema to Queen Elizabeth because of the crisis provoked by her uncle Edward VIII’s Abdication in 1936, but in a world where only at the weekend Grand Duke Henri, 69, the head of state of Luxembourg, paved the way for his son and heir Guillaume, 42, to take over his duties, will that always be the case for 75-year-old King Charles?

Naruhito’s father, now 90, became the first Japanese Emperor to abdicate since 1817.

‘It’s not that it was thought impossible but it was unthinkable for a Japanese Emperor to abdicate,’ Dr Prescott said.

Last week, Naruhito acknowledged some of the problems his monarchy faced before he left for the UK. But he avoided suggesting any solutions.

He said: ‘Currently, there is a declining number of male Imperial Family members and an aging population.

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 Japan’s Emperor Naruhito and Empress Masako arrive at Stansted airport on Saturday afternoon, with members of the RAF and UK officials on hand to greet them

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The couple were due to come to the UK on an official state visit in 2020 – but their plans were put on hold by the pandemic

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Empress Masako, 60, looked elegant in a powder blue suit with white lapels and a coordinated hat

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The couple, who both studied at Oxford University as students, looked delighted to finally be on UK soil

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The Japanese Emperor said this week that the late Queen treated him ‘like family’ when he was a young student in the UK

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Queen Elizabeth escorts Naruhito through the Great Hall in Windsor Castle, 2001

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The then Japanese Crown Prince Naruhito and Prince Charles watch an exhibit after the opening ceremony of the Japan Festival 1991 at the Victoria & Albert Museum

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Naruhito walks through Windsor Castle with Queen Elizabeth and Prince Philip in 2001

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The then Crown Prince Naruhito and Prince Charles attend the opening ceremony of the Japan Festival at the Victoria & Albert Museum in 1991

‘Female members of the Imperial Family lose their imperial status upon marriage, leading to a decrease in the number of royals able to engage in public activities compared to before.

‘This is a matter that relates to the future of the Imperial Family, but I would prefer to refrain from commenting on institutional matters.’

Instead this week he will focus on the job of showcasing closer trade and defence ties between his country and Britain.

The state visit was originally scheduled for 2020 when the UK and Japan signed a post-Brexit free trade agreement but had to be postponed because of the Covid-19 pandemic.