A no-holds-barred exposé on the financial transactions of the world's favourite sport

The transfer fees clubs pay to sign top players now top €4 billion a year but much of the money has been flowing out of the game. A small group of wealthy investors including Russian oligarchs, English racehorse owners and a former billionaire gold miner have seized the opportunity to enter this booming market.

Some have moved in on the territory of banks and lent money to clubs in exchange for a share in fees generated by Cristiano Ronaldo, Neymar and dozens more of today's stars. Others have acquired obscure teams to get a piece of the pie.

Even as the global financial crisis sent fortunes tumbling this select group found a profitable place to park their money. The size of the transfer market has continued to rise –- it increased seven-fold in value the last two decades, more than the FTSE share index.

Between them, these wealthy investors have amassed hundreds of millions of euros in profits. At the same time, they have managed to stay out of the spotlight the world's most popular sport brings.

Football's Secret Trade follows the money along a trail very few know about, from nondescript offices in the U.K. and ramshackle stadiums of South American clubs you have probably never heard of to offshore bank accounts in the Caribbean. Warning – you won't see a major transfer deal in the same light again.