Capital gains on shares that were held in trust

I have sold shares which were inherited from trust from a deceased grandparent and need to pay CGT for these. The shares were purchased in the trust therefore i have no way of knowing their purchase date or value. I do have the information regarding the trust value on the date it was transferred to me. Do I calculate the gain from the market value of the shares when transferred from trust or from the book value of the shares upon transfer to myself?

Hi ,
 

It will be the date they were transferred to you  .

Thank you .