Merge People Tags

[Mick Sulley]

Just discovered that I have a person tagged with two different names, 
'Jim Smith' and 'Jim Smith Jnr' in different pictures.  How can I merge 
them?  I tried editing the 'Jim Smith' tag but it won't let me give it 
the same name as the other, which is reasonable.  Is there away to do 
this other than going through each picture individually?

I have looked in the manual but cannot see how to do it.

Thanks

Mick