Is it possible for a person to cash out shares/currency in this scenario and not pay any CGT?

[foxmccloud]

I was thinking about CGT and the following scenario occured to me. It all happens in the same year:

A person buys shares/ foreign currency. The price goes up a lot and they make £1 million. They then exchange a part of that holding for another share or currency. Thus they need to pay CGT. E.g. they made a gain of £100k after that sale. They owe £20k tax.

However then the price of the new asset falls a lot and then they sell this asset for another one (share or foreign currency again), and they now have a loss of £90k. This offsets the £20k tax they had to pay. They still have a loss of £70k I believe?

Now the price of the this third asset goes up and they want to cash it out or perhaps cash out a part of the original £1 million they earned. Can they offset what they gain with the £70k loss? E.g. they sell the asset for £50k GBP, do they not have to pay any CGT for that year?

[foxmccloud]

I have realised that the above example is falwed. Please ignore it.