LONDON: Mining mogul Anil Agarwal pocketed just 6% profit from his 3.5 billion pound ($4.3 billion) investment in Anglo American, held since 2017, even though the underlying shares rose over 50% since then, according to Reuters estimates.

Agarwal's family vehicle Volcan Investments, the biggest shareholder in Anglo, said on Thursday it would unwind its almost-20% stake in the South African miner by repaying debt with 247.1 million Anglo shares.

After paying back the loan, Volcan would have been left with a 1.9% stake that was sold in the open market for 519 million pounds on Thursday. This makes up his gross profit from the whole investment, according to a source familiar with the deal.

Once coupon payments and the investment banking fees are accounted for, the sum dwindles to 196.25 million-213.7 million pounds, or 5.7%-6.1% of the original deal size, a Reuters calculation shows.

Under the terms of the original deal, Volcan borrowed 3.5 billion pounds through the issuance of a mandatory convertible bond arranged by US investment bank JPMorgan to fund the acquisition.

The convoluted structure, dubbed "POEMS" (Purchaser of Equity via Mandatory Securities) by JPMorgan, is a variation of the more traditional "exchangeable bond" format, where a borrower issues debt that can be converted into shares of another company.

Volcan Investments and JPMorgan declined to comment.

The first bond would have matured in April 2020, if the Indian billionaire had not cashed out, dashing speculation that he was preparing to take over the 30.8 billion pound diversified miner.

The nature of the convertible bond issuance, however, meant that Agarwal's profit was just a fraction of the London-listed miner's massive increase in value of an average 7 pounds per share over the past two years.

Agarwal's gross profit is the 24.7 million shares, or about 1.9% of Anglo, he was left with after repaying the bond. JP Morgan arranged a sale of those shares for 519 million pounds on Thursday.

On top of that, there is the 4% coupon paid on the debt, which comes at about 280 million pounds over a two-year period, and the fees paid to JPMorgan.

M&A consultancy Freeman Consulting Services said convertible bonds issued by Anglo American typically garner fees of around 0.75%-1.25% of the transaction size.

Assuming JPMorgan charged Volcan a similar fee for this convoluted structure, the total cost to Agarwal is 26.25 million to 43.75 million pounds.