CGT on inherited property. 50% in one year and another 50% in another year, how to calculate.

hi I inherited 50% of a house in 2005 , valuation at time was £415000 for entire house, and then inherited the remaining 50% in 2017, valuation was £66500 for entire house. The house is now being sold and under offer for £820000...I have never lived in the house, it was occupied by a relative. Do I need to do two calculations for the cgt liability...e.g. No.1. increase from 2005 to 2024 and No.2 increase from 2017 to 2024. These two calculations added together would give me the total gain am I correct with this approach...thanks.

Hi,
You take your share when initially acquired in 2005 and then again in 2017. added together, this is your purchase price to then work out any gain due.
Thank you.