Sheikh Mansour Bin Zayed al-Nahyan is a multibillionaire in his own right. He is also a member of a family whose wealth is estimated at more than $26 billion (£16 billion). He is the half-brother of the President of the United Arab Emirates and ruler of Abu Dhabi, as well as a full brother of the Crown Prince of Abu Dhabi, which makes him one of the most influential sheikhs in the Gulf.

It is these family connections that are rumoured to be behind Sheikh Mansour's purchase of shares in Barclays. He is thought to be acting for the al-Nahyan family as it invests its oil-generated fortune. Two months ago Sheikh Mansour bought Manchester City Football Club for £200 million and he spent a further £3.5 billion for a 16.3 per cent stake in Barclays.

It is unlikely that either the Emir of Abu Dhabi or the Crown Prince would allow themselves to be publicly associated with these investments because Arab royalty usually avoids any close association with money.

If Sheikh Mansour has become the al-Nahyan's family investor, they could not have chosen a better connected man. He is married to Sheikha Manal bint Mohammed bin Rashid al-Maktoum, the daughter of the ruler of Dubai, and is Abu Dhabi's minister of presidential affairs.

He is also chairman of the Abu Dhabi Petroleum Investment Company and chairman of First Gulf Bank, one of the region's fastest-growing banks.

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