Why would someone cross out White British on an ethnicity monitoring form and put Celtic/Pictish instead? And should I just mark him as White/British on my computer anyway?

And why the hell does the NHS Trust I work for collect ethnicity data in the first place? I've always found the "we're going to ask you your ethnicity to make sure we don't discriminate against your ethnicity which we could not do if we had not known it" approach a tad odd...