Research from Gallagher and the Centre for Economics and Business Research estimates that cyberattacks cost large UK firms £11.7bn last year. This total included £5.4bn in direct losses from disrupted trading and £3.7bn in shareholder litigation costs. Lost assets such as intellectual property totalled £1.3bn.

Laura Parris, executive director of financial lines at Gallagher, said: "For years, boards have measured cyber risk in terms of system downtime and IT recovery however the risk doesn't end when the attack is over. As the high-profile attacks on high street retailers last year show, the legal, financial and reputational fallout can drag on for months. In the US, breaches have gone even further, triggering costly shareholder lawsuits focused entirely onboard oversight and disclosure. With cyber governance under growing scrutiny, our research shows UK boards are not immune to losses on a similar scale either.

"Many organisations take comfort in the fact they have cyber insurance in place. But as the risk profile evolves and becomes more complex, having a policy is not the same as being fully protected. If boards aren't actively testing how their cyber and directors’ and officers’ insurance respond to cyber-triggered claims, they may find that the liabilities that hurt most are the ones that aren't fully insured."