CGT on sale of joint property

I purchased a flat that was my main residence before I began to let it out. I understand that should I transfer it into joint names with my wife when we come to sell we each have a CGT liability. My gain is between the purchase date and disposal date on 50% subject to a proportional PRR for the period I lived there. My wife's gain is between the value she acquired her share when it was transferred into joint names and the disposal date. If there is no change in value between the date of transfer and date of sale then is it correct she has no gain and no CGT? Thank you, any link to guidance would be much appreciated.

Hi BJ Ley,
Your wife will work out her gain the same as you.
Their gain will be calculated on the difference in value between when you first owned the asset and when they disposed of it.
Please see 
Capital Gains Tax: what you pay it on, rates and allowances
Thank you.