Silly insurance question

My car insurance ends on the 21st of this month. When it ends I'll have held my licence just over a year and will have 1 year NCB. I'm not renewing as I have a new car and will be selling my current one. I want to take out insurance on my new car today to start on the 21st as thats 21 days early (earliest I can do it so cheaper). Obviously at the time of the policy starting I'll have been driving a year and have my NCB. But at the time of taking out the policy I don't. How does this work?