I am a big fan of Red Dwarf although, in my view, the last series has not been quite as good as all the previous ones. However, this is a chicken and the egg situation. If our time traveller had researched properly he would have seen that he got arrested and therefore not done what he had done to get arrested. But this in turn would alter the timeline again and so he would not know that he had got arrested etc, I think I will just shut up now before it gets too complicated although there is a theory that says there are an infinite number of parallel realities. In the above case the time traveller by his knowledge of what he had done and so altering it would just progress along a different timeline. Star Trek did this in one episode when some anomoly caused an ongoing number of Enterprises to start appearing in the same universe and with that I will end.
Isn't this the guy in Jail for insider dealing who was supposed to be a Guru on ADVFN yesterday? The thread still went ahead but I assumed the thread was a April fool.
On a (slightly) more serious note, the fact that the market fluctuates in the way it does has been suggested as proof that time travel backwards is impossible! Of course this goes to the heart of the time traveller paradox, since any trading would cause the market itself to change rendering the type of time travel in which you could then predict the future impossible.