South Africa tax treaty

Hi, I am UK resident and hold South African shares subject to SA-UK DTA tax treaty. My broker does not reduce dividends withholding tax payable to the South African government from 20% to 10% (inline with the tax treaty). in this this respect, am I able to claim the full 20% deducted from dividends paid as a tax credit? Is there any further detail that needs to be supplied to HMRC for this purpose? Thank-you.

Hi,
Please refer to guidance at:
Tax on foreign income
Thank you