Unlike his brothers, who left for Southern Italy, Serlo remained in Normandy and inherited his father’s possessions.
On one occasion, Duke Robert was besieging a castle called Tillières, on the border between Normandy and France.
[3] Serlo (who was still in Brittany) was told of this, and, refusing to withstand the shame brought upon his people, he traveled to Tillières accompanied by two squires.
Serlo fought and killed the French soldier, parading through the Norman camp with his severed head on a spear, before returning to Brittany.
At this point Duke Robert sent an envoy to find out who killed the French soldier, and upon discovering that it was Serlo, he pardoned him and welcomed him back into Normandy.