What info does betfair use to exclude your account? (games)

You know when you select to be excluded from the games from 6 x months, and then a year or so later when you try to play you are still excluded and can only get 'un-excluded' via a physical letter. Well...

Does anyone know what info they use to exclude an account ? I have multiple accounts, some with old addresses and bank details etc, but all of them are excluded.

Anyone know what they use ? Surely not just your actual name and date of birth as there could be duplicates ?