The White Ship disaster set up a succession crisis for Normandy (Henry I always considered himself a Norman who happened to also be King of England) which would later lead up to The Anarchy.
Let's say the White Ship Disaster didn't happen. William, hier apparent, is charismatic and popular. His sister becomes widowed and was married off to Geoffrey Plantagenet count of Anjou in May 1128 (so both of Henry I's children are married into the Anvegins). Geoffrey kisses up to and impresses the Norman counts (he didn't try to do this until 1140s in OTL, long after many of the Normans threw in their lot with Stephen)
Then in June 1131, all the people involved in the OTL white ship disaster plus a few extra make their way towards Rome for... I dunno a vacation. Meanwhile, there is a civil war where two counts in southern France were fighting over something. Unexpectedly, the Normans and their entourage are killed, apparently mistaken for one of the factions despite not being fully prepared for war and not having the banners of the other side. Stephen of Bolois (one of the "few extra"), a knight from the household, and his wife were the only ones to escape. Stephen is pissed off that the counts were willing to endanger the women and children in the entourage.
In September 1131, a few documents were recovered by the Normans. They show without a doubt that letters were issued by the Steward of Louis, King of France, to contain the power of Geoffrey Plantagenet "directly or through his allies, and his majesty gives full power to use lethal force is nessary" was given to one of the two counts in France that were fighting.
Louis stays silent on the manner, not condemning the letter. The Norman party finds proof the letter came from Louis's court, they know it's not fake (imagine whatever proof you want, just that anyone looking at the letter and also seen Paris can't dispute it). Most of France except Brittainy, Anjou, Bolois, and Normandy accuse the Normans turning a tragedy into a framing opportunity.
Henry I goes into shock and isn't seen outside his personal quarters for a month. When he comes out, he seems mostly normal and have recovered his mental health, except that he insists the letter must have come from a "fake Louis court" and his liege couldn't have possibly ordered the death of William. Except for this one denial, he seems 100% sane. He gives 7 key castles in Normandy to Matilda and Geoffrey and asks the Normans to make his daughter the heir to England and his daughter and son-in-law co-hires to Normandy.
Matilda is pissed she didn't want to be the Queen. While she enjoys the prestige she had as Empress from her first marriage and being Queen is prestigious, she would rather have her bother alive, on the throne, and get a fief from him than sit on the throne herself. Matilda gathers her husband and some Normand counts and asks how she can force Louis to apologize when Louis isn't even admitting responsibility. When the Pope was asked to excommunicate Louis, he simply said "uhhh... Normans were the victims of a heinous crime and it's clearly a conspriacy. Someone in Louis's court, possibly himself, is responsible. Everyone pray for the Normans and I hope the whoever is responsible confesses his sins"
Like the OTL white ship disaster, the Normans not only lost their heir, but the crème of the nobility (every important family had at least someone on that ship). In TTL, they lost their boys and antagonized their liege by (factually correctly) accusing his court of plotting against them. And most of the rest of France refuses the irrefutable evidence.
Let's say the White Ship Disaster didn't happen. William, hier apparent, is charismatic and popular. His sister becomes widowed and was married off to Geoffrey Plantagenet count of Anjou in May 1128 (so both of Henry I's children are married into the Anvegins). Geoffrey kisses up to and impresses the Norman counts (he didn't try to do this until 1140s in OTL, long after many of the Normans threw in their lot with Stephen)
Then in June 1131, all the people involved in the OTL white ship disaster plus a few extra make their way towards Rome for... I dunno a vacation. Meanwhile, there is a civil war where two counts in southern France were fighting over something. Unexpectedly, the Normans and their entourage are killed, apparently mistaken for one of the factions despite not being fully prepared for war and not having the banners of the other side. Stephen of Bolois (one of the "few extra"), a knight from the household, and his wife were the only ones to escape. Stephen is pissed off that the counts were willing to endanger the women and children in the entourage.
In September 1131, a few documents were recovered by the Normans. They show without a doubt that letters were issued by the Steward of Louis, King of France, to contain the power of Geoffrey Plantagenet "directly or through his allies, and his majesty gives full power to use lethal force is nessary" was given to one of the two counts in France that were fighting.
Louis stays silent on the manner, not condemning the letter. The Norman party finds proof the letter came from Louis's court, they know it's not fake (imagine whatever proof you want, just that anyone looking at the letter and also seen Paris can't dispute it). Most of France except Brittainy, Anjou, Bolois, and Normandy accuse the Normans turning a tragedy into a framing opportunity.
Henry I goes into shock and isn't seen outside his personal quarters for a month. When he comes out, he seems mostly normal and have recovered his mental health, except that he insists the letter must have come from a "fake Louis court" and his liege couldn't have possibly ordered the death of William. Except for this one denial, he seems 100% sane. He gives 7 key castles in Normandy to Matilda and Geoffrey and asks the Normans to make his daughter the heir to England and his daughter and son-in-law co-hires to Normandy.
Matilda is pissed she didn't want to be the Queen. While she enjoys the prestige she had as Empress from her first marriage and being Queen is prestigious, she would rather have her bother alive, on the throne, and get a fief from him than sit on the throne herself. Matilda gathers her husband and some Normand counts and asks how she can force Louis to apologize when Louis isn't even admitting responsibility. When the Pope was asked to excommunicate Louis, he simply said "uhhh... Normans were the victims of a heinous crime and it's clearly a conspriacy. Someone in Louis's court, possibly himself, is responsible. Everyone pray for the Normans and I hope the whoever is responsible confesses his sins"
Like the OTL white ship disaster, the Normans not only lost their heir, but the crème of the nobility (every important family had at least someone on that ship). In TTL, they lost their boys and antagonized their liege by (factually correctly) accusing his court of plotting against them. And most of the rest of France refuses the irrefutable evidence.