Mary Queen of Scots' half-brother killed her husband in bid to seize power - as letter by Elizabeth I may have solved 450-year murder mystery 

• Historian claims husband of Mary, Queen of Scots was killed by her half-brother 
• Professor Kate Williams suggested new theory behind unsolved 450-year-old 
• She claims Lord Darnley was murdered by Mary's sibling James, Earl of Moray  

A leading historian claims to have solved a 450-year-old murder mystery and identified the culprit who killed Mary, Queen of Scots' husband.

Professor Kate Williams, a bestselling author and professor at the University of Reading, has suggested that Lord Darnley was murdered by Mary Stuart's jealous half-brother James, Earl of Moray.

Her theory comes to light ahead of the release of one of the most anticipated historical dramas of the year, Mary, Queen of Scots starring Saoirse Ronan as Mary Stuart and Margot Robbie as Elizabeth I.

Accounts hitherto suggested that Lord Darnley was murdered by his kinsmen while historians claimed he died at the hands of the rebel Queen's third husband, the Earl of Bothwell.

Mary, Queen of Scots was also implicated in the savage murder. 

Their marriage had been under serious strain since they wed in 1565, and just two years later he and his squire were found dead in an orchard in Kirk o'Field, Edinburgh. 

But now drawing on letters written by Elizabeth I and the lords, Professor Williams claims one suspect who went under the radar was Mary's half-brother, James, Earl of Moray. 

Not long before the bodies were discovered, an explosion had rocked Lord Darnley's home but it is believed the blast was detonated after the murder, a possible attempt to cover the real cause of death. 

Professor Williams told MailOnline: ‘The Earl of Moray was a suspect at the time but he was simply too powerful so squashed any suspicion.

‘He was Mary’s fathers’ illegitimate son with a mistress, which normally wouldn’t have got you very far in those situations but with him it did - he was the leader of all the Lords and aristocracy.

‘He continually tried to get power off of her.

‘After various attempts of trying to take power –abduction, war, kidnap – The Earl of Moray knew he had to push her out of the way and be this Regent de facto king before her baby son.

‘Everyone hated Lord Darnley because he took their land away, such was the power he had being married to the Queen.’

Professor Williams said Lords plotted to kill Mary’s husband Lord Darnley under the orders of the her half-brother.

‘The night before the murder, the Earl of moray conveniently disappeared to go and ‘look after his ill wife’ - then came back the next day.

‘They found Lord Darnley with his servant smothered in a nearby orchard on February 10.

‘Beside them was a chair, rope and dagger and two dressing gowns because Darnley and his servant had heard gunpowder being planted at the house so escaped using the chair, rope and dagger. They were wearing dressing gowns because they had been in bed.

‘But they only got so far before they were strangled by henchmen.

‘All of this was part of big conspiracy by the Earl to take power. They said he ‘look through his fingers when it was done’, ie, assenting to the murder.

Mary realised what had happened and was terrified. She knew the Lords and her half-brother were a part of it but she was powerless. They directed suspicion to her. Moray sidelined Mary and got all the power for himself, imprisoning her and forcing her to abdicate.

‘She made the fatal mistake of rushing to England thinking Queen Elizabeth would put her back on the throne. Elizabeth was in a quandary - she was sympathetic and didn’t want Queens to be undermined but the Earl of Moray was simply too powerful.

‘She was in an impossible position.

‘This was the perfect crime. Moray got everything - but then of course just got shot - power is a dangerous game.’

In 2015, a panel assembled by the Royal Society of Edinburgh was convened to consider the crime with modern investigative methods - and it concluded that Mary's hands were clean. 

The congregated experts include pathologists, explosives experts, scientists and historians. 

The inquiry appeared to exonerate Mary, but was inconclusive on cause of death, and the precise identity of perpetrators remains unknown.

Professor Williams is the author of Rival Queens: The Betrayal of Mary, Queen of Scots, which is in bookshops now. 

Mary Queen of Scots, will be in cinemas on Friday.