There are two types of protection that may be available to protect your no claims bonus.
Step back protection applies automatically once you have 3 or more years no claims bonus. In the event of a claim, you will not lose your full bonus, but it will be reduced.
Protected no claims bonus If you pay extra to protect your no-claims bonus once you have 3 years or more no claims bonus, you can have two claims in a three-year period of insurance without affecting your no-claims bonus. This does not protect your premium.