Anti-Slavery International's Beth Herzfeld told the BBC earlier this year that chattel slavery, involving a class of hereditary slaves, still existed in parts of Africa, and bonded labour remained common in South Asia.

BBC: Undated depiction of slaves in captivity

In the early 1990s, Pakistan introduced the Bonded Labour System (Abolition) Act, including imprisonment and fines for offenders, and in the past has responded to CNN's reporting on the issue by listing the practical measures it's taken to protect workers.

CNN: 'Humans of New York' takes on bonded labor in Pakistan

Carrying the defence brief in opposition, he bonded with his Labour opposite number, Bob Ainsworth, over their shared struggle to persuade their party leaders to take the military's low morale and underfunding more seriously.

ECONOMIST: The defence secretary