Calculate Capital Gains for shares for USA broker in USD

Good day, Thanks a lot for providing answers and references. I was trying to find answer for next questions related to capital gains happened person who used USA based broker in USD currency. Let's imagine that capital gain was made at USA based broker in USD currency. Could historical exchange rate from https://www.exchangerates.org.uk/ be used to calculate GBP value for such capital gains? Let's imagine that shares was sold on 15 of December 2023, but actual exchange to GBP currency happened only on 15 of February 2024. Is it possible to use exchange rate for actual currency exchange for whole lump sum in case? Or that is a requirement to calculate capital gains by using exchange rate on sell date? Could capital gain be calculated originally in USD [(SellPrice - Acquire Price) * Number of Shares] and only that result converted into GBP? As opposite to calculate every Sell / Acquire Price in GBP by using historical currency exchange rate and make final calculation totally in GBP?

Hi Ivan Sidarau,
You can use any of the exchange rates that apply for that tax year -  HMRC currency exchange average rates - GOV.UK (trade-tariff.service.gov.uk) 
Thank you.