Can I just point out that a formal assessment of capacity may not be needed unless the lpa (if there is one) makes it a requirement.
The reality is, assuming that there isn't such a requirement, if (for example) a person is in a care home because they aren't safe in their own house and has no understanding that 1) they need to be there and 2) the house needs to be sold to pay the bills, it's entirely likely that no formal assessment of capacity will be required.
Edit: in fact a registered lpa is often used as a general poa for people who have assets in the UK but who reside overseas where there is no hint of dementia or lack of capacity. I doubt that's what is going on here, but it's important to note that without restrictions written into it, a registered lpa for finances may quite possibly be used when the donor still has capacity. The remedy if the donor has capacity and doesn't care for the attorneys actions is to revoke the lpa.