CGT when not on the deeds

Hello, I have inherited a 7th of a property in Portugal from my grandmother. She died a Canadian/Portuguese citizen and her will is in Canada. The property has been transferred into my aunts and uncles names but once it is sold I will inherit one seventh of the sale value as per the will. The capital gains tax in Portugal is 28%, and since my name is not on the deeds themselves (only the Canadian will), I have been asked that my tax share is reduced from my monetary inheritance instead of me paying the Portuguese government the taxes owed. If I proceed, how do I prove to the UK government that I paid CGT already to avoid double taxation? Do I even need to declare it as capital gains from the sale of a foreign property, or simply a monetary inheritance not subject to any CGT at all? It will only be between 8-12k EURs.

Hi,
This would be a monetary inheritance and not liable to Capital Gains Tax.
Thank you.