Got this from the Business Link website:
Professional indemnity insurance
If you are in the business of selling your knowledge or skills, you may want to consider taking out professional indemnity (PI) insurance.
What you will be covered for
PI insurance protects your business against claims for loss or damage by a client or a third party if you have made mistakes or are found to have been negligent in some or all of the services that you provide for them. PI insurance will also cover legal costs.
Many professions are required to have PI insurance cover as a regulatory requirement or as a result of their professional authorisation. This includes solicitors, accountants, architects, mortgage intermediaries, insurance brokers and financial advisers. Many consultants, advertising and PR agencies, and designers also choose to have this type of insurance.