How Tostig Godwinson’s brotherly betrayal hastened the fall of the Anglo-Saxons

Tostig, long overshadowed by his brother Harold, would ultimately become both an instigator and a victim of one of the most consequential years in English history – a moment explored in the new BBC series King and Conqueror.

Who was Tostig Godwinson?

Tostig Godwinson was the younger brother of King Harold Godwinson, the king who lost his crown (and life) to William the Conqueror at the battle of Hastings in 1066.

Through his support of the Norwegian king Harald Hardrada, Tostig helped to hurry the two invasions of 1066, that weakened England’s defences and left the country vulnerable to Norman conquest.

Tostig as Earl of Northumbria

Tostig’s place in the story of 1066 is inseparable from the extraordinary power of his family. His father, Godwin of Wessex, rose from obscurity to become the most influential noble in England: so powerful that when he and his children were exiled by the king, Edward the Confessor, in 1051, popular pressure forced their return within a year. It was a clear signal: the Godwins rivalled the authority of the crown itself.

When Godwin died in 1053, Harold took his place as the Earl of Wessex, effectively becoming second in power only to the king.

Tostig gained the earldom of Northumbria two years later in 1055, when Earl Siward – a loyal supporter of Edward and a powerful figure of Danish descent – died without an heir.

Though a southerner, Edward appointed Tostig to fill the position, likely due to his family’s clout at court rather than local popularity.

What is certain is that Tostig’s rule in Northumbria was troubled from the start.

The region had strong Scandinavian ties and operated with a degree of autonomy. Its aristocracy was unused to southern interference, and Tostig’s governance quickly bred resentment. He was accused of levying oppressive taxes, implementing unfamiliar laws and executing nobles without due process.

By October 1065, dissatisfaction boiled over into open rebellion. The revolt was led by local magnates and thanes, – including Gamelbearn; Dunstan, son of Æthelnoth; and Glonieorn, son of Heardwulf – who had deep roots in the region’s ruling elite.

They stormed York, killed Tostig’s supporters, and declared him outlawed.

Why did Tostig betray his brother Harold?

The rebels sought support from Harold Godwinson – and rather than defend his brother, Harold negotiated with the rebels, ultimately agreeing to replace Tostig as earl.

This was likely out of a desire to prevent a wider civil war on the cusp of an expected Norman invasion. King Edward, old and ailing, was reportedly enraged by Harold’s actions but ultimately bowed to necessity. Tostig was replaced as earl by Morcar, brother of Earl Edwin of Mercia, in a concession to northern demands.

Tostig viewed Harold’s actions as a profound betrayal, but for Harold, the preservation of national stability outweighed familial loyalty. With the kingdom under threat from multiple foreign claimants, the spread of rebellion in the north was a dangerous distraction.

Tostig’s offer to Harald Hardrada

Furious and humiliated by his toppling and by being abandoned by his brother, Tostig was forced into exile.

First he travelled to Flanders, where he had family ties through his wife, Judith, daughter of Count Baldwin IV. He sought aid from European courts to reclaim his earldom, approaching William of Normandy, who was preparing his own claim to the English throne, but found no welcome there.

Tostig ultimately turned to Norway, offering his support to King Harald Hardrada.

For Tostig, this formidable Norwegian monarch served both a path to revenge and a chance to return to power. For Harald, the timing was fortuitous.

Hardrada was an infamous warrior-king who had spent his youth fighting across Europe, from the Byzantine empire to the lands of the Kievan Rus. A half-brother of King Olaf II of Norway, Harald had fought at the battle of Stiklestad (1030) and spent years as a mercenary in the Varangian Guard before returning to claim the Norwegian throne in 1046.

He ruled as a fierce, autocratic monarch, feared in Scandinavia and renowned across Christendom. His own claim to the English throne derived from a tenuous but not implausible agreement: in 1038, Harthacnut (son of Cnut the Great and Emma of Normandy) and Magnus I of Norway had supposedly agreed that if either died without an heir, the other would inherit his kingdom.

When Edward the Confessor died childless in January 1066, triggering a bitter succession crisis, Harald viewed it as an opportunity to revive this claim.

His purported promise to Duke William of Normandy years earlier aside, Edward had not named a clear heir, and there were multiple potential claimants to the throne. The Witenagemot – the Anglo-Saxon council of nobles – chose Harold Godwinson, Earl of Wessex, as king.

He was crowned swiftly, but two fearsome rivals quickly emerged: William, claiming Edward had promised him the crown, and Hardrada, citing his Norse inheritance rights stemming back to Cnut.

Hardrada didn’t actually press his claim until approached by Tostig. Tostig’s offer of support, and his inside knowledge of the Anglo-Saxon state and infrastructure, made the proposition suddenly irresistible. So, with both set to gain, the two men forged a mutually advantageous alliance.

In September 1066, they launched their invasion of England.

Stamford Bridge: Tostig’s revenge backfires

Harald and Tostig landed near York and defeated local forces at the battle of Gate Fulford on 20 September, killing hundreds of English troops. They then demanded hostages and supplies, expecting little resistance.

But Tostig’s brother Harold, displaying remarkable speed, force-marched his army north and took the Norwegian host by surprise at Stamford Bridge on 25 September.

Accounts describe a dramatic clash: the English fought across a narrow bridge, with one giant Norse warrior said to have held it singlehandedly before being felled from below. But, having been caught unawares, Harald and his men were roundly defeated.

Hardrada was killed in the chaos (arguably bringing the Viking Age to an end with him), and Tostig, refusing to yield, died fighting beside him.

Had Hardrada succeeded, Tostig would likely have been restored as Earl of Northumbria, possibly even elevated further in gratitude. But, in the long-term, he likely would have been in considerable danger. As a Godwinson, and a brother of Harold, Tostig would have been a rival to deal with; not a vital ally for support.

In the end, Tostig’s grand ambitions and feud with his brother died with him at Stamford Bridge.

Yet if his true aim was to bring about his brother’s downfall, he did ultimately get his wish at Hastings, even if he didn’t live to see it.

1066: The battle for England

Member exclusive | The year 1066 is the most famous in English history, but there's a lot more to the story than one bloody battle at Hastings. In this four-part series, medievalist Marc Morris talks David Musgrove through the full story of the Norman Conquest.

Watch all episodes now

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