Crown Princess Mary has put on an elegant display in a stunning bespoke gown by a Danish designer at a glittering evening reception in New Delhi on Tuesday night. 

The 51-year-old future queen of Denmark and her husband Crown Prince Frederik are on an official visit to India taking in Agra, Delhi and Chennai.

They are joining a delegation of Danish business representatives on a tour designed to strengthen trade and industry ties between the two countries, with a focus on green energy. 

For the final night on Tuesday, the mother-of-four put her best sartorial foot forward in a bespoke rust-coloured gown by the Danish fashion designer Soeren le Schmidt.

Princess Mary accessorised with a floral jasmine arrangement in her hair and large gold earrings, both of which pay tribute to the host country. 

A 'gajra' is a flower garland that is worn by South Asian women during festive or special occasions, weddings, or as part of everyday traditional attire.

Princess Mary completed her outfit with nude stilettos and a gold bangle.

At the dinner, representatives from 38 Danish companies were present, as well as the Danish Foreign Minister Lars Løkke Rasmussen, Environment Minister Magnus Heunicke and Climate, Energy and Supply Minister Lars Aagaard.

The dinner rounded off a successful trip to India, in which the royal couple met President Droupadi Murmu, who took them on a tour of the presidential palace and gardens.

They also laid a wreath at the memorial for Mahatma Gandhi, a revolutionary who was assassinated in 1948, and visited other Indian landmarks including the Taj Mahal.

The India trip comes after the couple had to step up their royal duties as Frederik's mother, Queen Margrethe of Denmark, is recovering from major back surgery after being in pain for 'quite some time'.

The 83-year-old monarch had an operation on February 22 after consulting with doctors, a statement on the Danish royal family’s official website read.

'For quite some time, Her Majesty has been affected by problems with her back, and the situation has worsened recently,' the palace said ahead of the surgery. 

'After consultation with Rigshospitalet’s specialists, The Queen has decided to undergo extensive surgery. 

'The operation is planned for... Rigshospitalet in Copenhagen, where The Queen will also be hospitalised afterwards.'

They added: 'Consequently, a longer sequence of physical rehabilitation is expected. 

'This means that Her Majesty's official program in the near future will be postponed, cancelled or handled by other members of The Royal Family.'

Queen Margrethe is now the longest-ruling monarch in the world after the death of Queen Elizabeth II. 

FITNESS

One of the ways in which Princess Mary stays looking fit and young is through a targeted exercise regime that includes walking, jogging and horse riding.

'Mary, like the rest of her family, is totally dedicated to exercise. She's always walking, jogging, or riding a horse,' her sister-in-law Leanne Donaldson previously told New Idea.

This was in full evidence during the Princess's recent family trip Down Under for Christmas, when Mary was spotting both jogging around Sydney with her son and diving headfirst into the waves at Palm Beach.

Over the years, Princess Mary has been spotted trying her hand and succeeding in a number of sports, from tennis to charity fun runs.

She also reportedly has a personal trainer to help her stay in shape.

DIET

When it comes to her diet, reports suggest that the Australian-born royal has the 'Danish diet' to thank for her long, lean physique - a regime that is centred on locally sourced and readily available natural foods.

'People living in Denmark tend to eat more fish, especially oily fish like salmon and less meat than a typical Western diet,' Sydney-based dietitian Lyndi Cohen previously told FEMAIL.

'In the "Danish diet", the emphasis is on high quality meats when meats are eaten - and lean options.'

A closer look at the regime shows the Danes typically have a lower intake of carbohydrates and a higher intake of good fats like nuts and seeds and protein.

'The Danish diet includes fruit and encourages snacking on berries, which are high in antioxidants that can protect against disease,' Lyndi said.

'It also includes plenty of root vegetables like carrots, parsnip and potatoes, while rye bread is a staple food in the diet - principally because it it much higher in nutrients like the B group vitamins, Iron, phytochemicals and magnesium.'

'Rye also contains considerably more fibre than white options, which can support a healthy and heart health,' she said.

The dietitian explained if Princess Mary is following the 'Danish diet', then she is likely to be snacking on plenty of fruit and vegetables and eating lots of oily fish, potatoes, nuts and seeds and cheese.

However, while Mary is disciplined, she is not overly so, as the Princess has been spotted regularly enjoying lavish dinners and glasses of red wine.