Russian energy firms have made a lot of money this year despite sanctions against the country, because the invasion of Ukraine and subsequent sanctions have pushed up the price of oil and gas on the global market.
In the early days of the conflict BP announced plans to get rid of that stake, gave up its two seats on the Rosneft board and wrote off the value of the investment in its accounts.
The campaign group Global Witness said that BP should be entitled to 580 m - a sum it claims is equivalent to more than a third of the direct financial assistance provided by the UK to Ukraine.
In his letter to the BP chief executive, seen by the BBC, Mr Ustenko cited this figure and pointed out that because BP is still a Rosneft shareholder, it is owed the money.
BP will receive the money from a restricted Russian bank account, which is a clear indication of the historic mistake your company has made, but all the same, BP will receive the dividend, he wrote.
It stressed that it had already written off investments worth more than $24 bn 20 bn and no longer reported any income from Rosneft, reducing its stated earnings by some $2 bn a year.