In 1980, the order of succession was changed.
Prince Carl Philip, then not even a year old, was no longer intended as heir to the throne, but Crown Princess Victoria.
A decision King Carl XVI Gustaf still does not quite agree with.
- Having laws that work retroactively is not wise, I still think so.
My son Prince Carl Philip was born and then suddenly they change so he gets rid of it all.
It's quite strange, I think, says the king in the documentary series "Sveriges sista kungar".
Göran Ellung is the producer for the documentary.
- I was surprised when he took such a strong stand.
When it happened, you can understand that he had some thoughts.
Now 40 years later, and with all the changes that have taken place in society, I think it is very remarkable.
"Actually goes against the constitution"
The interview was the first of two with Sweden's monarch.
- When the interview was finished, the king was satisfied and I was satisfied.
The next day the court called and wanted a new interview, they said they wanted to clarify what the king thought about the order of succession.
So it was a new interview, but it was basically the same answer.
No big difference, says Göran Ellung in SVT's Aktuellt.
For the king to say this, can it in any way go against the constitution?
- If you ask political scientists, very little has been written about his role.
It is often said that he should be apolitical and not think things.
But the king may think, it is not at all that he is free of opinion.
Man, he shouldn't have an opinion that goes against what the government believes, that's where the line is.
Basic laws are passed by the Riksdag and the government and in this case he is actually going against what the constitution says.
It states that the eldest child, regardless of gender, shall inherit the crown.
Sweden's last kings is published on SVT Play Sunday 8 January at 02.00 and broadcast on SVT1 Thursday 12 January at 20.00.