They allege traders shared information about the planned block trade without first securing Segantii's agreement not to trade, a process known as wall-crossing.
The case centres on a series of trades around the Esprit share sale and tests how sensitive deal information was handled between the bank and the hedge fund.
Is the Segantii trial a simple case of insider dealing, or does it expose a broken 'honor system' across banking?
With insider trading now threatening prediction markets, are regulators fighting yesterday's war while losing tomorrow's?