You might think that an accident resulting in a claim for £5M would take some arranging but this is far from the case as the link provided above shows, albeit a motoring one. Bear in mind also that, in the case that a £10M payout results and you only have £5M cover then you are 50% underinsured and the insurers may therefore pay out only a commensurate 50% of their maximum liability under the policy, ie a far from adequate £2.5M. You and your colleagues could well be approached for the remaining £7.5M ! How much is your house worth ?
Irrespective of the above potential woe, if you are super-rich or, alternatively, a man of straw, you can probably sleep easy at night regardless. But that leaves most of us to fret a bit, I suppose. Suggest you ask your insurer how much extra per £1M of liabilities .. and then get a bold group decision on the final figure !
Caveat aviator
(but it'll probably never happen).
SI