Last Friday, when it was announced that Volkswagen had agreed a takeover of Porsche, with a little help of money from Qatar, it seemed that this saga was nearing the end. No so.

After German prosecutors raided to Porsche offices in Stuttgart on Thursday looking for evidence of “market manipulation” and a violation of “disclosure rules” the whole thing now looks set to run and run.

So, what are they looking for? You may recall Volkswagen shares soared last October when the much smaller Porsche announced it had bought a majority stake, catching everyone off guard.

Many people in the markets had “shorted” the stock (basically a bet the shares would fall) and had to quickly try to buy shares, even as the price took off, in order to cover their exposure. Then, almost as quickly, the shares fell hard.

German stock market rules stipulate how many shares an entity can purchase (percentage wise) of another company before having to disclose that position to regulators. But apparently the same rule does not apply when it comes to share options (an option to buy shares at a certain price).

Porsche had built up a huge number of options, to the surprise of the market, and apparently to regulators.

No matter how this investigation plays out, some in Germany hope there will be a change in the law to cover options, to limit the chances of this happening again.

Of course, the Porsche position did not work. Volkswagen is going to gobble up the premium car maker.