He is a little-known actor, with few important roles to his name.
And in terms of media profile, there is virtually none as he has even deleted his Instagram account.
Yet he has been named one of the world’s most eligible bachelors by society bible Tatler and will one day inherit the entire 13,500-acre Althorp estate where Diana, Princess of Wales, grew up.
When his father – Diana’s brother Charles – dies, Louis Spencer will assume his title and become the 10th Earl Spencer.
Lady Eliza Spencer, Louis Spencer, Viscount Althorp, Victoria Lockwood and Lady Kitty Spencer at Prince Harry’s wedding to Meghan Markle at St George’s Chapel in May 2018
Earl Spencer, brother of Princess Diana, with his children: Amelia, Eliza, Kitty and Louis at the official opening of the Princess of Wales Memorial Playground in Kensington Gardens in 2000
Louis, who was born on 14 March 1994 at St Mary’s Hospital, London, is the only son of Princess Diana’s brother Charles Spencer, 9th Earl Spencer, and his first wife, Victoria Aitken
Viscount Althorp and Prince Harry at the wedding of Celia McCorquodale and George Woodhouse in June 2018
With it comes the magnificent Grade I-listed Georgian house and grounds, estimated to be worth more than £100m.
With its 90 rooms, extensive collection of prized art and furniture – and 28 listed buildings and structures on the grounds – Althorp in Northamptonshire has been the family seat of the Spencer family for more than 500 years.
Today, Louis, who lives in London, turns 30. Although he has three older sisters, the male primogeniture means that he will be the sole heir to this fortune.
Louis, who already holds the title of Viscount Althorp, is the youngest child and only son his father had with his first wife, Victoria Aitken (née Lockwood).
Born on 14 March 1994 at St Mary’s Hospital, London, he was raised by his mother in South Africa following his parents’ split. While living in Cape Town, he studied at the city’s most expensive private school, Diocesan College, where fees cost the equivalent of £13,955 a year.
He later returned to the UK to study at the University of Edinburgh.
Tall like his cousins Princes William and Harry, Louis went on to study acting at ArtsEd drama school in Chiswick, London. He performs under the stage name Louis John Lyons and is signed to the Tavistock Wood talent agency, whose stars include Dominic West and Lily James.
Unlike her older sisters Lady Kitty, 33 – who has also modeled for Dolce & Gabbana – and twins Lady Amelia and Lady Eliza, 31, who have been Tatler cover stars, Louis avoids social media and high-profile events.
Tatler described the strawberry blonde heiress as ‘tall, debonair and very beautiful but ‘super private’.
And the Daily Telegraph last year went so far as to dub Louis ‘the reluctant poster boy of male primogeniture’.
Earl Spencer, 59, has spoken out to say he will stick to tradition and choose Louis as his heir.
In 2015 he said: ‘If I chose Kitty it would be against all the tradition that goes with Althorp. It’s just the way it is. I get the problems with it as a concept.
‘I also get the strength from the fact that it has worked to date. It is still intact. If you go around the castles of the Loire or whatever, they’re empty.
‘Everything is shared equally through the generations and you end up with a beautiful building with one beautiful tapestry in it. The whole idea of primogeniture was to hold it together.’
Louis has a close relationship with his sisters.
He walked his eldest sister Kitty down the aisle at her Italian wedding in place of their father, who controversially did not attend.
As children, they had enjoyed a privileged but private upbringing in Cape Town, where Earl Spencer and Victoria moved in 1995 to raise their children out of the public eye.
The couple divorced in December 1997, months after Diana’s death, and Charles moved back to the UK soon after.
Apart from a handful of photo calls with his father, Louis has largely stayed out of the limelight.
His first high-profile appearance was at Prince William and Kate Middleton’s wedding in April 2011, although the 17-year-old was outshone by his glamorous blonde older sisters.
Four years later, Louis unexpectedly appeared on rapper Nicki Minaj’s Instagram feed.
He was seen with his arm around the American star, with the singer cheekily writing “check out our wedding photo”.
Louis first came into the spotlight at Prince Harry and Meghan Markle’s wedding in 2018, when he accompanied his mother and sisters.
Dapper in a morning suit, Louis became one of the unlikely stars of the day and received dozens of playful marriage proposals from concerned social media users.
Louis Spencer and his mother, Victoria Aitken, at Tatler’s English Roses 2017 at the Saatchi Gallery in London
Thanks to male primogeniture, Louis will one day inherit the house of Althorp
The Spencer family pictured at the 10th anniversary memorial service for Diana, Princess of Wales at the Guards Chapel, Wellington Barracks in August 2007
Louis walked his eldest sister Kitty down the aisle with their half-brother Samuel Aitken at her Italian wedding – instead of their father
Their close sibling relationship is said to be partly due to their private upbringing in Cape Town
Apart from a handful of photo calls with his father, Louis has largely stayed out of the limelight
His appearance and strong family resemblance also earned him the nickname ‘Harry Lite’.
No doubt his family connections and looks will come in handy if Louis decides to pursue his dream of becoming an actor.
In 2019, his father Charles Spencer revealed: ‘Louis lives in London. He is an actor at the drama school and works incredibly hard, and I want him to be able to fulfill his dreams in that direction. It’s full: he works 14-hour days.’
However, it remains to be seen how he can juggle a burgeoning career with the considerable responsibility of managing Althorp when the day comes.