Robin Hood Tax Propose Mythical Banker Taxation

Here's a screenshot from a new widget from the Robin Hood Tax campaign:

So a 100% Tax on something worth £7.2 billion would raise £7.2 billion for public spending, would it?

Short answer: No.
Long answer: Noooooooooooooooooooooooooo.

Here's some content harvested from Wikipedia:

A 100% tax rate will also generate no revenue because at such a rate there is no longer any incentive for a rational taxpayer to earn any income, thus the revenue raised will be 100% of nothing.