Capital Gains on Residential Rental Property owned jointly but originally bought in sole name

My partner (now husband) bought a 50% share of my rental property several years after I bought it in my sole name. He paid 50% of the market value at the time of purchase. When we come to sell, what figures do we use as individuals to calculate our gains? Thank you

Hi,
If you were unmarried at the time, he would use the amount he acquired 50% for.
Thank you.