A property was initially used as a client's private residence. It was then used as a business asset and, several years later, became his private residence again.
The property was, therefore, either his private residence or his business property, but was never used simultaneously for both.
I am aware of the anomaly in the interaction between taper relief and principal private residence relief but I understood that this only applies where there is mixed use at the same time (with, for example, shops, pubs etc). Indeed, Sch A1 para 9 CGTA 1992 is headed "cases where an asset is used at the same time for different purposes".
The tax inspector is claiming that the mixed use provisions apply in this case and I'm claiming they don't.
Any confirmation of the position (favourable or otherwise) would be appreciated.