The paper says that despite commissioning a private poll before the referendum which showed a Remain vote winning, Hanbury, who works for renowned fund, Odey Asset Management, decided to gamble on a Leave vote anyway - reasoning that there was a lot to gain and little to lose.
The Mail adds that Hanbury's father is a close "hunting friend" of Prince Charles and that he grew up in a 250-room Leicestershire mansion.
Odey Asset Management - which runs funds worth $10.2 billion (£7.6 billion) - is one of a few asset managers who scored big time in the wake of Brexit.
The NuWave Matrix Fund was up 12% last Friday while Quadratic Capital Management reported its best returns since it launched. Schonfeld Strategic Advisors, which manages about $12.5 billion worth of funds, also enjoyed a big boost.
Brexit has hit the financial world hard, with the pound dropping to a 31 year low and billions disappearing from the FTSE in the days after the result. But the markets have recently rallied back, with the FTSE 100 reaching 6,365 points this afternoon.
Many have predicted the prolonged uncertainty could still hurt the City of London - with Vodafone already threatening to move jobs abroad and Goldman Sachs predicting that many banks will follow suit.
The uncertainty is not helped by the fact that both of the main parties are currently having a leadership crisis, with no word on how Britain will actually manage its exit from the EU. Conservative frontrunner Theresa May has said the referendum results must be respected and that Britain will leave the EU whatever happens.