The wealthy aunt of Syria’s brutal dictator was secretly granted the right to live in the UK after she promised to invest millions in this country, The Telegraph can disclose.

Her two grown-up children - first cousins of Bashar al-Assad - were also allowed to stay.

The woman and her two sons are the wife and children of Rifaat al-Assad, dubbed the ‘Butcher of Hama’, who earned his nickname after allegedly ordering the killing of up to 40,000 Syrians in 1982.

Rifaat, 80, is the uncle of Bashar al-Assad and owns hundreds of properties in France, Spain and the UK, many of which have now been seized. According to recent reports he is facing corruption charges in France.

The decision to give his fourth wife, aged 63, indefinite leave to remain in the UK was made in 2012 at the height of the Syrian civil war and when Theresa May was home secretary. Her two sons, now aged 22 and 37, were allowed to stay at about the same time. Another son of Rifaat, but who has a different mother was granted indefinite leave to remain in 2014. Rifaat has four wives and is thought to still be married to all of them.

Rifaat, who served as head of Syria's feared Defense Companies paramilitary unit in the 1970s and 80s, went into exile in Europe after a failed coup against his brother Hafez, Bashar’s father, in 1984 although he was Syria's vice president until 1998.