Selling arms to a country such as Saudi Arabia – an oil-rich, absolute monarchy that spends three times the developing country average on its military and does not distinguish between public budget and privy purse – is hugely profitable.

Allegations by the BBC and Guardian newspaper that BAE Systems paid £1bn to Prince Bandar bin Sultan, son of the Saudi defence minister and crown prince, for facilitating the £43bn Al-Yamamah deal, Britain’s biggest export order, may indicate just how profitable.