Aviva may as well just be doing this for the George family. REUTERS/Denis Balibouse One French investor owns a financial contract so good that most people wouldn't believe it exists. It gave him 68.6% returns every year from 1997 to 2007, and he is exposed to almost no risk at all.

That man is Max-Hervé George, who is the subject of an amazing FT Alphaville piece, and his deal with a major insurance company may be the best in the world.

When George was 7 years old his father bought him a life-insurance contract that allowed him to switch his investments based on their market prices published each Friday. He can switch those investments at any time in the next week based on those prices, regardless of what happens to them during the week.

It is almost unbelievable. Here is how it works, according to the FT, which called it a "magic ticket":

Life insurance is a popular savings product in France, and typically the customer allocates their money among different investment funds offered by the insurer. But this contract was not typical: prices for the funds were published each Friday, and clients were allowed to switch funds at those prices anytime before the next price was published, even if markets moved in the meantime.

L'Abeille Vie called this an arbitrage, but really it was a gift. Is the stock market up this week? Just call your broker to buy it at last week's price and pocket the difference ...

Mr George continues to arbitrage time. For instance, he might have his money in an Aviva fund invested in the French stock market. Lets say the Nikkei 225 rises 5 per cent during the week. He'll tell Aviva to move his investments into its Japanese fund, at the price before the market moved.

If George's investments crash, no problem: He can just move them into something that didn't crash. Aviva is legally bound and has to accept this. George has to deliver instructions by letter, which he makes sure is done by a bailiff.

The contract is an artifact of a bygone age in which financial price data was not readily available to anyone with a computer and switching your investments took time. The company that sold it, Abeille Vie, was merged into Commercial Union, which was then merged into Aviva. Aviva France is still bound to the contract.

George and his family have won at least three court battles to keep the deal. As of 2007 the family had €21 million ($23.53 million), of which €1.4 million belonged to Max-Hervé. That's from just €8,000 worth of French francs initially. As for how much the family has now, Alphaville have crunched the numbers:

Estimating the size of his windfall is an illustration of exponential growth. Assume the growth rate of 68.6 per cent a year continues, and €1.4m becomes €93m. There was quite a significant market crash in 2008, but imagine you were able to pick the best performer each week as markets rebounded in 2009.

By 2020 that would be €1.2 billion, and over €230 billion by the end of 2030 (at which time it would be worth more than Aviva). Take a look at the whole article over at the FT, because it is absolutely amazing.