I can't be bothered trying to find my children's b/cs to check. Does this mean that the certificate number and the NHS number were one and the same within that time frame?
What about people not born in 'England'? Where do their NHS numbers come from? Over to you to answer that one Scouseboy .....
Just had a quick read of that Wiki article - is that true about the numbers and the calculations which have to be added and divided and add up to a certain number etc?

It's an oddly written article.