Deloitte, the world's biggest accountancy firm, helped in falsifying documents to hide Roman Abramovich's wealth and evade tax, a BBC investigation has found.
BBC Panorama and the Bureau for Investigative Journalism uncovered hundreds of documents that were falsified and backdated to conceal his wealth and evade tax.
Roman Abramovich denies any wrongdoing.
Watch the investigation into how Abramovich hid his fortune on BBC iPlayer.