From attacks on voters rights to tobacco companies denying responsibility for their products, every controversial lawsuit has one thing in common: lawyers, fighting on their client's behalf.

After all, the right to counsel is a central plank of the legal system. If you are accused of a crime, you will be represented by someone who knows the law.

But as the world's biggest law firms have grown larger and more powerful, has their success changed their relationship with politics and the law?

David Enrich is the business investigations editor at the New York Times, and in his new book, Servants of the Damned, he looks at the power these firms wield and explores how they came to wield it.