Oxfam have launched a petition asking David Cameron to take action to crack down on tax havens and the many other tax avoidance tricks used by multi-national corporations and the superrich. This is part of Oxfam's wider international campaign about inequality. They calculate that 62 people have as much wealth between them as 3,200,000,000, or half the world's population. London as one of the leading centres of global finance, accounting and business must have a major part to play in rebalancing our world. The people at the very top are taking too much, and if you read Professor Sir Michael Marmot's book 'The Health Gap', you can see in detail how everyone, from rich to poor, would benefit from a more equal London, a more equal Britain, and a more equal world.
Oxfam's petition is here https://act.oxfam.org/great-britain/en
There's a good review of 'The Health Gap' here. https://www.timeshighereducation.com/books/review-the-health-gap-michael-marmot-bloomsbury