Not just for insurance either. Any job application, any financial product application and any legal documentation that requests info on criminal records have to be declared for 5 years after conviction. The rehabilitation of offenders act (ROA) states after this, you are not required to declare.
The only real anomalies to this are if a job requires an enhanced DBS check, or if you are applying for a travel visa when you are required to confirm criminal records, even those that are spent under the ROA. Some job applications ask if you have ever had received a criminal record, generally though they are not supposed to ask this and any spent convictions can be ignored despite their asking.