Hi,
Yes, you do. You would need to obtain the value of gold at the time you received the gift and using the weight of the gold, calculate the value of the gift. This value should be converted to GBP sterling using an exchange rate appropriate to the date of the gift. The disposal value and disposal costs should also be in GBP sterling, so that the difference can be calculated. If there is a gain, then you may have Capital Gains Tax to pay. You can see guidance here:
Capital Gains Tax on personal possessions
Under the terms of Self Assessment, we do not provide an official exchange rate and the onus is on the individual to use a just and reasonable exchange rate for each acquisition and disposal. For your convenience, there are exchange rates here:
Exchange rates from HMRC in CSV and XML format
and for older rates here:
Foreign exchange rates and spot rates: 1 January 1989 to 31 March 2009
You are free to use any of the supplied rates or one of your own choosing.
Thank you.