Counts Nikolai and Felix of Denmark make a dashing return to public life as they attend Princess Isabella's 18th birthday after being stripped of their titles

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Princess Isabella of Denmark was the star of the show on Tuesday evening as she attended a theatre performance as part of her 18th birthday celebrations. 

The royal, who is the eldest daughter of King Frederik and Queen Mary, celebrates her actual birthday on April 21, but has already embarked on a glamorous slew of celebrations. 

She looked as stunning as ever in a sparkling navy gown and matching clutch, with her locks pulled back into a sleek bun, as she arrived at the Royal Danish Theatre's Old Stage in Copenhagen. 

She was accompanied by her mother Queen Mary, 53, and twins Princess Josephine and Prince Vincent, 14.

Mary was elegant as ever in an off-the-shoulder black and silver ensemble, with a glittering skirt and brooch catching the eye.  

Meanwhile Isabella's very dashing cousins, Count Nikolai, 25, and Count Felix of Monzepat, 22, the sons of Prince Joachim, were also in attendance, wearing velvet suit jackets with smart bow-ties. 

King Frederik meanwhile appeared very dapper in a royal blue suit. 

Tensions had risen between the family in 2023, after Queen Margrethe stripped Prince Joachim's four children - Nikolai, Felix, Henrik and Athena, of their titles - but, as they beamed on arrival, any feelings of resentment appeared long gone. 

Counts Nikolai, 24, and Felix, 22, were as dashing as ever at Princess Isabella's 18th birthday celebrations

Denmark's Princess Isabella, King Frederik X, Queen Mary, Crown Prince Christian, Princess Josephine, and Prince Vincent arrive

At the time, Margrethe insisted the move would be 'good for them in their future' and allow the children - who have maintained their positions in the line of succession - to 'shape their own lives without being limited by the special considerations and duties' that a formal affiliation with the Danish Royal Family involves. 

But Prince Joachim publicly spoke out against his mother's decision in the days that followed - claiming that his children had been 'harmed' in the process. 

Nikolai has since launched his own Instagram account to promote his modelling career - and has seldom been seen with his cousins and aunt since the announcement. 

Last weekend, Princess Isabella delivered her first solo address at a celebration in honour of her coming of age.

The Princess, who officially turns 18 over Easter on April 21, was joined by her parents and younger twin siblings Princess Josephine and Prince Vincent at the city hall in Aarhus to attend the first of two major public birthday celebrations.

Much to the delight of royal fans, the Danish princess took to the podium at the conclusion of the formal proceedings to deliver her first official address as a royal.

And surprisingly, Princess Isabella chose to dive into her debut speech with a cheeky and self-deprecating joke.

'Almost four years ago I found out that your words can be overheard when you least expect it,' Princess Isabella said, as the room erupted in laughter.

Princess Isabella was joined by her beaming mother Queen Mary

Count Nikolai gave a friendly wave to crowds as he arrived at the event

Princess Isabella beamed as she received a bouquet of flowers

Mary was elegant as ever in an off-the-shoulder black and silver ensemble, with a glittering skirt and brooch catching the eye

The Danish royals attended the birthday performance at the Old Stage at the Royal Danish Theatre

Isabella looked stunning in a glittery navy dress with elegant puffed skirt

King Frederik, Queen Mary at a birthday performance at the Old Stage in the Royal Danish Theatre in Copenhagen

The royals waved to crowds after attending the performance, which comes ahead of Isabella's 18th birthday

'Today I have no doubt that the microphone is on.'

The bold comment referenced a terse moment in 2021 when Princess Isabella was caught on camera saying the words 'are you completely confused' to her mother, Queen Mary.

The teenage princess' frustrated statement was made following her brother Prince Christian's confirmation as the royal family tried trying to arrange themselves for a family photo outside the church - with the candid mother-daughter exchange captured in a viral video.

According to local Danish publication Billed Bladet, the unexpected opening line in Princess Isabella's speech instantly captured the audience's attention.

Danish publication BT's entertainment editor Fie West agreed, praising the young royal for making such a bold opening statement.

'Princess Isabella shows great initiative by starting her very first official speech with a joke,' Fie said.

'She speaks into something that many Danes remember and have brought a smile to their faces, and it is extremely charming that she displays self-irony,' the entertainment editor added.

The celebratory event held in honour of Princess Isabella's upcoming 18th birthday saw her gifted flowers, a book filled with personalised greetings and a lavish piece of jewelry, which was presented to her by the mayor of Aarhus, Anders Winnerskjold.

After the unexpected introduction, Princess Isabella went on to thank all the attendees at the special birthday celebration, while also highlighting her own personal connection to the Danish city of Aarhus.

'Dear mayor, dear Aarhus, dear everyone who has come today. Thank you so much for a very special birthday celebration,' she said.

'It makes me really happy to be celebrated in a city that has great significance for me and my family.'

'Here I have celebrated Christmas, Easter, walked by the water and in the garden and enjoyed myself in the old town since I was little. I have many good memories in Aarhus and today I have another one.'

The lavish birthday event, which was projected to cost upwards of 290,000 Norwegian Kroner, equivalent to about AU$70,000, featured an extravaganza of performances including dance and music displays and even a fashion show.

The young royal was also presented with three elaborate birthday cakes made by students studying at Aarhus Tech.

The Princess made sure to give a special 'thank you' to all the talented and hard-working people who had contributed to the occasion.

The daughter of Queen Mary, 53, and King Frederik, 56, also thanked the crowd for the 'nice piece of jewellery', which according to the pre-party itemised budget was estimated to be worth 10,000 kroner, equivalent to around AU$2400.

Princess Isabella (centre) attended the celebratory birthday event in Aarhus alongside her parents Queen Mary (second from right) and King Frederik (second from left) and 14-year-old twin siblings Princess Josephine (far right) and Prince Vincent (far left). Her older brother Prince Christian was unable to attend as he's currently serving in the national service

The Princess was also touched by the sentimental gift of a book filled with personalised greetings and well-wishes.

The royal concluded her inaugural speech by saying: 'That you have chosen to celebrate me and that so many have come makes me happy and touched. You should know that it means a lot to me. Thank you very much.'

This celebration is the first of two events arranged by the Royal House ahead of Princess Isabella turning 18.

Next up, the princess will be celebrated with a birthday performance on The Old Stage at the Royal Theatre in Copenhagen.

The Princess and the royal family have invited over 1000 young people from across Denmark to join them to watch the special performance being held this coming Tuesday.

A royal household statement reads: 'The Royal House of Denmark, in cooperation with The Royal Danish Theatre, invites the young generation to entertaining, exciting and varied performing arts that are both classical and modern.'

The performance is also set to be broadcast live on local television network DR, so all Danes can watch from their living rooms.

The upcoming milestone birthday will also see Princess Isabella receive a major honour from her father King Frederik, known as the Order of the Elephant.

The royal household have just released Princess Isabella's new 18th birthday portraits

Although she technically won't receive the Order of the Elephant until she turns 18 next week, it is expected that Isabella will wear the insignia for the first time at the Royal Danish Theatre performance.

The royal household have also recently released new birthday portraits of Princess Isabella to mark her coming of age.

The royal's 18th birthday pictures were taken by photographer Steen Evald in Frederik VIII's Palace at Amalienborg.

On her actual birthday on 21 April, Princess Isabella is expected to enjoy a private birthday celebration with family and loved ones.

From this year onwards, Princess Isabella will also have her birthday added into the rotation of annual flag days, which are the official dates when the national flag is traditionally flown.