I will try my best. Thanks for the interest. Kiddie language for a Brit:
Let’s say Portfolio 1 is worth 15,000 GBP in total. It owns 500 Harry Potter shares worth 2 GBP each. This makes the Harry worth 6.67% of the overall, i.e. (500*2)/15,000
Portfolio 2 is worth 20,000 GBP and also has 500...