Mr. Peter Lennon:

It called up my PPSN, my name, date of birth, etc. The IHI is the last link in the chain, as it were. Given that the IHI has a database underpinning it, which includes the PPSN, I imagine that sometimes it seems rather convoluted by when the legislation was enacted in 2014, the IHI was at the apex of what was called an identifier data set.

It is what a GP would hold, which is name, date of birth, sex and nationality. It includes the PPSN. The IHI is the remaining component that must be put in.