Normandy event?

[Kelthor]

So, during a game a while ago, I noticed that Rollo is in the game at 867, just that he's unlanded at the start. I picked him up as a courtier, and while I was rummaging around in England, I decided to invade the duchy of Neustria, and subsequently granted it to him. Now, at some point, there must have been an event where he creates Normandy, as I wasn't paying attention, but all of the sudden it had changed. So I'm guessing there's an event of sorts? Thing is that I've never managed to get this event to trigger again. What are the pre-requisites?

[Ashling]

Decision name: Establish Norman Culture

Effect:

• Change culture to Norman
  
  
• Norse and French culture characters in the Northern France region change culture to Norman
  
  
• Culture gains all innovations discovered by the Norse and French cultures
  
  
• Duchy of Neustria is renamed Duchy of Normandy

Requirements:

• At peace
  
  
• Own and fully control the Duchy of Neustria
  
  
• Norse culture
  
  
• At least one county de jure part of Duchy of Neustria has French culture
  
  
• No Norman culture exists

Edit: at least that’s what it says on the wiki.[ck3.paradoxwikis.com]

[Kelthor]

Originally posted by Triangle:

Decision name: Establish Norman Culture

Effect:

• Change culture to Norman
  
  
• Norse and French culture characters in the Northern France region change culture to Norman
  
  
• Culture gains all innovations discovered by the Norse and French cultures
  
  
• Duchy of Neustria is renamed Duchy of Normandy

Requirements:

• At peace
  
  
• Own and fully control the Duchy of Neustria
  
  
• Norse culture
  
  
• At least one county de jure part of Duchy of Neustria has French culture
  
  
• No Norman culture exists

Edit: at least that’s what it says on the wiki.[ck3.paradoxwikis.com]

Thank you! I kinda wonder why I didn't find this myself. It's kinda cool that the AI apparently can trigger events with such specifics by itself.