“In 1297 the famous William Wallace, the hammer of the English, the son of the noble knight Malcolm Wallace, raised his head.....When Wallace was a young knight, he killed the sheriff of Lanark, an Englishman who was dexterous and powerful in the use of arms, in the town of Lanark. From that time therefore there gathered to his side like a swarm of bees all those who were bitter in their outlook and oppressed by the burden of servitude under the intolerable rule of English domination, and he was made their leader.”
Scotichronicon, Book 11, Chapter 28
No one really knows what happened that night in May, 1297 in Lanark. According to Blind Harry’s popular version of events, Wallace responded to insults from English soldiers when he was leaving St Kentigerns church one Sunday morning. Initially, he ignored their taunts, but, when they said that his daughter had been fathered illegitimately by a priest of the chapel of St Nicholas who had been sleeping with Wallace’s wife, his temper snapped. A brutal running street fight ensued and Wallace's men joined in, leaving fifty Englishmen dead or dying in the streets. Eventually, weight of numbers forced Wallace and his followers to retreat to the family house of Wallace’s wife, Marion Braidfute. There, they continued a futile resistance until a decision was made to retreat to the nearby Cartland Crags outside the town walls.
The men fought their way out but Marion was not so lucky. Heselrigg, the Sheriff of Lanark, was outraged by the carnage and was determined to wreak a brutal vengeance upon Wallace. He had Marion executed immediately in the town square. When the news reached Wallace, he was beside himself with grief. But he bided his time and planned his attack on Lanark Castle slowly and methodically.
The English garrison soon sank into complacency thinking that Wallace and his rebels had been cowed into submission. But Wallace gathered his small force at Cartland Crags and stealthily infiltrated the town in ones and twos. By nightfall, they were all inside the walls. Then, silently through the darkness, Wallace and his followers crept up to the castle and quickly overpowered the guards. Minutes later they had gained access to Heselrigg's apartments and Wallace bounded up the stairs to kick Heselrigg’s bedroom door open. Startled from the depths of sleep, Heselrigg was unable to defend himself and Wallace split his skull to the collar bone with his massive two handed sword. Heselrigg's son, hearing the commotion, rushed up the stairs to his father's bedroom only to be cut down himself. As Wallace hacked Heselrigg’s corpse to pieces, others of his band spread throughout Lanark to assassinate other English officials and sympathisers.
It is impossible to find definite facts about Wallace’s attack on Lanark and his slaying of the Sheriff. For instance, nobody really knows whether this Marion Braidfute actually was Wallace’s wife.
Perhaps a more reliable account can be found in the Scalacronica, written by Thomas Grey, whose father was actually present during the incident. He wrote that a fracas broke out at a court being held by Heselrigg, but Wallace was able to escape with help from a girl who may have been his wife or mistress. He came back later at night with some supporters and attacked Lanark, killed Heselrigg, nearly killed Thomas Grey senior, and set fire to some houses. The Scalacronica states:
“At which time  in the month of May William Wallace was chosen by the commons of Scotland as leader to raise war against the English, and he at the outset slew William de Hesilrigg at Lanark, the King of England's Sheriff of Clydesdale. The said William Wallace came by night upon the said sheriff and surprised him, when Thomas de Gray, who was at that time in the suite of the said sheriff, was left stripped for dead in the mellay when the English were defending themselves. The said Thomas lay all night naked between two burning houses which the Scots had set on fire, whereof the heat kept life in him, until he was recognised at daybreak and carried off by William de Lundy, who caused him to be restored to health.”
This was no minor skirmish, Wallace’s sack of Lanark is regularly cited as being the event that sparked the subsequent Scottish Wars of Independence. Wallace and his band apparently killed two hundred and forty soldiers, merchants and commoners, sparing only the women and priests. Wallace was a young man at this time and, unfortunately, it is not known why he was at Heselrigg's court. Blind Harry has him named as an outlaw in more than one district following a succession of lethal brawls with the English occupiers so he may have been on trial for some incident. It is also intriguing to wonder whether this was a spontaneous incident or whether it was carefully co-ordinated with other risings which were occurring all over Scotland at that time.
There is no doubt that he did indeed attack the town and kill the Sheriff, however. At his trial in Westminster Hall on 23rd August 1305 a lengthy list of his “crimes” against the English were written into his indictment. Within that list was included the following statement;
“……The aforesaid William Wallace, forgetful of his fealty and allegiance, raised up all he could by felony and premeditated sedition against the same lord the King, having united and joined to himself an immense number of felons, and he feloniously invaded, and attacked the Guardians and ministers of the same King, feloniously and against the same lord the King's peace, insulted, wounded and killed William de Heselrigg, sheriff of Lanark, who the appointments of the said King in the regular meeting of the county court, and afterwards in contempt of the same king without reason fought against the same sheriff whom he had killed………”
William Wallace was dragged from Westminster Hall immediately after the conclusion of his show trial and brutally murdered at the Elms at Smithfield.