It is unlikely to happen, according to BBC legal affairs analyst Jon Silverman.
BBC News website's Katherine O'Shea looks at the handful of cases in which it has been used in the past century.
1916 ROGER CASEMENT
The renowned human rights campaigner was convicted of high treason for his involvement in the Irish Nationalist revolt in Dublin.
He was hanged at Pentonville Prison.
Executioner Albert Ellis recalled: "He appeared to me the bravest man it fell to my unhappy lot to execute."
1945 JOHN AMERY
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