The Guardian has the best description of this very desirable tax based on the Tobin Tax idea. Bill Nighy looks wonderfully shifty in the famous video.
Joseph Stiglitz, professor of economics at Columbia University: “A tax structure that does not reward short-term, very speculative gains would be good. If you were investing for a year or five years or 10 years it would be a small tax but if you were holding it for just one minute it becomes a very high tax. The important question is implementability. It’s designed to tackle high frequency activity for which it is hard to find any societal benefit. The only question is, can it be effectively implemented? Will it be circumvented? There’s a growing consensus it can be implemented, if not perfectly, effectively enough to make a difference.” (link to article and video)