The rivalry between the 35-year-old stars stretches back 18 years to the time when they both fought to represent Great Britain in the Athens Olympics in 2004.
This time it was Amir Khan who got the chance, took Olympic silver but won the hearts of the British, and then became world champion as a professional already as a 22-year-old.
For almost two decades, he has been one of the big poster names for British boxing.
Kell Brook has also reaped great success and was, among other things, world champion between 2014 and 2017, but has nevertheless been overshadowed by the much-known Khan.
Last night, they met in front of 20,000 spectators in a sold-out and boiling Manchester Arena.
"The King of the North of England"
It was an entertaining match from the start with a lot of action and several tough changes.
Amir Khan, who is known for having a weak chin, was unwell already in the first round and stumbled backwards towards the ropes after Brook hit with a hard jab.
Khan responded well in round two and most of round three, but at the end of the third Brook stood for a violent forcing and seemed to be close to finishing the match.
Khan took more and more blows and when he defended himself worse and worse in the sixth round, the referee went in and broke the match.
The victory went to Brook via technical knockout and he thus improved his match result to 40 wins (28 on knock) and only three losses.
- What a feeling!
It is this type of mega-fights that you want to be a part of.
I finished Amir just as I said I would.
I'm the king of the north of England, Brook exclaimed.
The referee breaks the match in the sixth round.
Photo: TT
Brook wants to continue his career
Despite many harsh words over the years, not least the weeks before the match, the boxes met in the middle of the ring and embraced each other.
- I have always had respect for Amir, but I have never had anyone back.
It's hard to like a guy who just disses you year after year.
But I give him respect for this match and I have heard that he is a good guy.
Maybe we can have a coffee sometime, says Brook.
He admits that he has considered putting his gloves on the shelf, but says that this experience has given him the impetus back.
- We'll see what happens now, I have to talk to my family first, but I have three wonderful daughters who ask me for money sometimes and if the money is right, there are more matches for me to go.
I'm back!
The entertaining match is described as a challenger to "Match of the Year".
Photo: TT
Khan: "It was probably the end"
For Amir Khan, whose record falls to 34 wins and six losses, it may have been his last appearance in the ring.
- I have played 40 matches, won two world championship belts, boxed in the US and around the world.
I think this is the end of my career.
I do not have the same feelings for the sport anymore.
I felt that in the ring today and maybe it's a sign that I've done mine, says "King Khan".
And adds:
- I am very disappointed, but all respect to Kell who offered a fantastic effort and was the better boxer tonight.
Brook, from Sheffield, proclaimed himself "King of the North of England".
Photo: TT