Thousands of staff across dozens of London financial firms will be put through a “war games” scenario on Tuesday to test how well they can handle a major cyber attack, people familiar with the matter said.

In one of the largest exercises of its kind in the world, the test dubbed “Waking Shark II” will bombard firms with a series of announcements and scenarios, such as how a major attack on computer systems might hit stock exchanges and unfold on social media.

It will be co-ordinated from a single room housing regulators, government officials and staff from banks and other financial firms.

Hundreds more people are expected to be involved from their own offices as the “war game” plays out.

Simulations are likely to include how banks ensure the availability of cash from ATM machines or deal with a liquidity squeeze in the wholesale market and how well firms communicate and coordinate with authorities and each other.

There will be a particular focus on investment banking operations, one of the sources said.

Regulators and firms are growing increasingly concerned about the threat of cyber crime to the banking system, including the impact of coordinated online assaults or hacking attacks on specific banks and the Bank of England’s Financial Policy Committee has already told banks to strengthen defences.