Can you help with a problem I have very recently been presented with by my current insurer please?

I have been asked to prove that I have in excess of 9 years' NCD. My previous insurer only wanted detail of 5 years plus but Direct Line want 9 years plus, as this is what I entered into the computer. I have not had an accident, and therefore have not claimed on my insurance, since 1990.

I find that there is no loyality for staying with a provider hence I move each year to get the best quote. Until now I have been using online sites to get quotes where the options for NCD range from 1-5+ or 1-9+ years. Unfortunately I have not kept any old policy documents and cannot prove definitively that I have the NCD that I know I have.

I have 5+ and 9+ years' NCD, unfortunately the '+' has been lost into the land of noughts and ones. I feel that I am stuck between differing providers requirements where none of them actually keep a complete record. Any thoughts and or advice would be greatly appreciated.