A gain arising on a property which has been your private residence throughout your period of ownership is exempt from CGT. There are deemed period of occupation rules which may help to provide an exemption from CGT even if you were not living in the property at the time. This can with care result in obtaining the valuable relief on a 2nd home (as reportedly achieved by several of our MP’s!).
In particular, your last 36 months of ownership is treated as a period of occupation as a residence, but from 6 April 2014 this reduces to 18 months. Clearly timing is of the essence here.