How to declare savings interests in foreign currency

I have a Trading 212 account where I have uninvested cash giving me interests (in euros). How should I declare this amount in my self assessment? Should I convert it to GBP and add the amount to my UK saving interests? If yes, how do I know which exchange rate I should apply? If no, how should I proceed? Thank you for your help.

Hi Pierre,
This should be declared as foreign income and needs to be converted to sterling.
HMRC rates are at HMRC currency exchange average rates.
Exchange rates from HMRC in CSV and XML format
Thank you.