When you arrange a policy, you start off with zero no claims, as such it obtains the maximum premium, each year of no claims attracts a percentage until which point maximum no claims is reached at 60-70% dependent on the insurer. Should you have an accident and your no claims are not protected, then you would lose 20% of your no claims bonus. You would now only have 40-50% bonus dependent on the insurer. Then you also have the additional risk you now are which will load your premium anywhere between 15-25%. The two combined can cause a significant and marked increase in premium.

If you protect your no claims, you can make two claims in any three years underwritten period with the same insurer without it affecting your no claims. Each claim would load your premium, and the percentage deduction is applied. So your premium would still rise after claiming, but not as much. If you are a high-risk driver, driving lots of miles, commuting in traffic daily, live in a high-risk area, and are therefore are more likely to claim, then protect it. If you live in the sticks, are low risk, don't commute, then do not protect it. But it's all about personal choice.