Although this story may sound like another Sintra tale, part of it will be true. A legendary account of one of the scourges of the North, who coming down the Atlantic entered Sintra one day by way of the river at Colares, Sigurd the Viking, was king of Norway from 1103 to 1130. He was one of three sons of King Magnus III, all from different mothers, but although all bastards they had the right to the throne after their father's death.
In a great expedition of about 10,000 Norwegians and some Swedes and Danes led by King Sigurd himself, a young, brave and avid ruler of renown.
After wintering in England and wreaking havoc on the Galician coast - in the latter case, the events took place after the local governor stopped supplying the Nordic forces with adequate food and supplies - he then began raiding and pillaging the coast of al-Andalus, much in the style of Viking pirates, led by Sigurd, crusading to the Holy Land with nearly 60 ships.
Continuing their journey southwards, on current Portuguese territory, in 1109, Sintra, Lisbon and Alcácer do Sal were the next places attacked by Sigurd and his forces. As far as Sintra is concerned, it is very likely that the Nordic warriors went up the Colares river - once navigable - during high tide, and it was probably not the first time that Nordic forces had sailed in that branch of the sea.
He then went to the Fortress of Sintra, which was in the possession of the Muslims, and Sigurd decided to lay siege to it. A hard and difficult battle, but that the Norwegians won forcing all the inhabitants to embrace Christianity, those who refused were tortured and many "cut to pieces".
Sigurd also tried an attack on Lisbon, managed to loot the city and also won the battles in Alcácer do Sal.
They were hesitant between settling in the conquered lands or continuing their expedition to Palestine, but finally opted to abandon the lands and settlements and re-embark towards Gibraltar.
Certainly, the history of the Iberian Peninsula would have taken a different course if Sigurd had decided to settle permanently in the extreme (...) of Lisbon.
With the departure of the Norwegians the Moors were so weakened that, under threats, they consented to the vassalage of Count D. Henrique. He marched on the castle of Sintra, reducing it once again to obedience. After the death of the count and released from vassalage, it was only in 1147 that "the fortress of Sintra passed definitively from the possession of the crescent to the cross".
So says the Nordic saga that eternalised the deeds of Sigurd, although some details are rather doubtful and debatable. It is never too much to remember that the Nordic sagas, written long after the events and in poem form, mix memories of historical deeds with fables, praising the deeds of the Nordic kings and their warriors.
Sources: "Sintra Lendária" by Miguel Boim; Article found on Facebook