If you provide professional services to members of the public then you need professional indemnity insurance. To avoid taking it out is a false and dangerous economy. It is not expensive; you can even purchase it online.
The primary danger of avoiding professional indemnity insurance is that, should a claim be brought against you, then at the very least you could be significantly out of pocket and you could be financially crippled; you could even lose your business and your home. Regardless of your profession this is a good idea, pub landlords can take out pub insurance for example, whereas office owners can take out office insurance.
Modern society has become extremely litigious. It used to be the USA, but it is now just as bad in the UK. With many solicitors willing to operate on a no-win no-fee basis, people are encouraged to file a claim for the slightest of mistakes that might leave them out of pocket or emotionally distressed. However careful you are in your profession, everybody sometimes makes mistakes. Not all mistakes are the result of acting unprofessionally; many are just bad luck.
Some professionals are legally obliged to take out indemnity insurance, in particular financial advisors and accountants, and anybody who provides legal advice. It is often the condition of being a member of a professional group or society too. But for many people who work professionally with the public it is technically optional; though failing to take it out makes no business sense.
If a case is filed against you, even if you are found to be not to blame, the associated legal costs of proving your innocence could be disastrous. If you are found to be at fault and compensation is awarded against you, then in the worst case you could find your life has been reduced to tatters.
Any form of cost benefit analysis – however simple – will prove the worth of insuring yourself. It costs so little to take out in order to provide you with many millions of pounds worth of protection.