Hi Ki Chan,
I regret that we cannot comment on scenarios, real or imagined.
Non reporting funds are treated as 'offshore income gains' and are subject to income tax and not capital gains tax.
The gains should be entered in box 41 of SA106 and in the box marked "Other overseas income and gains" on the online return.
You can find more information here
IFM12300 - Offshore Funds: introduction: non-reporting funds