Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
Before I can respond to you question I need to know what sort of wrapper is involved. For example if you have invested in ISAs, Child Trust Funds and pensions then they will be free of Capital Gains Tax (CGT) anyway.
I have had a look at the prospectus for this fund and it is suspiciously slient as to the taxation position. It would not appear to be an ISA, a SIPP, or a Child Trust Fund.
Accordingly this 140K gain, 70K each, will be subject to Capital Gains Tax (CGT) on sale. However, if you have held these investment for a period of five whole tax years whilst non resident in the UK there will be no CGT payable except on the difference in value since your return to the UK and then you each have an Annual Exempt Amount of 11.1K to offset any gain. You would probably be better off realising any gain before you return to the UK, but you may be caught by any similar taxation levied in the country in which you currently reside.
I do hope that you have found my reply of assistance.
Thank you for your support.