I recently was involved in an accident (at fault but no other parties involved). I've tried to understand how the NCD works but is confusing from the same insurer.

So, my policy documents state: Protected no claim discount - maximum number of claims allowed - 2 claims in 3 years. But the same document goes on to show a table:
1 claim in next 12months - keeps NCD in same place
2 claims in next 12months - keeps NCD in same place
3 claims in next 12months - reduced NCD to 3 years.

I am not sure why the discrepancy of stating you can have 2 claims in 3 years but then goes on to state 12months?

Further, what happens if I move insurers next year - does this reset as you are with a new insurer, so 'allowed' 2 further claims in 3 years (or 12months)?