There are lots of strange things going on here.
A joint will is very odd indeed. Once it has been made then it can only be altered if both people agree to it.
So usually there are two, mirror, wills.
"A joint will was made before he lost capacity and daughter 2 was made executor.
Since then the will has been revised, daughter 1 has power of attorney."
Did he still have capacity when the will was altered? This is crucial. If he did not have capacity at the time then daughter 1 could only rewrite the will if she got a court order allowing her to do that.
- "can a joint will be amended without one partner having capacity and with only mum and poa present?"
To do this the person with the PoA would have to apply to the Court of Protection for an order along with medical evidence that the dad lacked capacity.
They cannot just write a new will on their own.
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- "if so can the executor be changed? Dad was adamant daughter 2 was executor"
As above, the PoA would need to apply to the Court.
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"Daughter 1 is talking about sharing out assets already to get in the 7 year inheritance tax rule whilst parents are still alive."
- "can money be dished out now with mums consent but obviously not dad's?"
Any assets that are purely in mum's name (eg if she has a bank account in her own name) then mum can do that with her own assets.
Any joint assets and it's a different matter. The PoA has a legal duty to act in the best interests of the person concerned. The LPA may have conditions in it about what the PoA is allowed to do.
However, I'm not sure that giving away assets would in any way be considered in their best interests. Also, if either of them were likely to go into care, which seems not unreasonable, then the local council may come after the PoA for deprivation of assets.
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- "who safe guards dad and all the assets when mum is now too old to be care anymore and trusts daughter 1 over everyone else?"
If there is a LPA for dad then it will be whoever is named in the LPA. If the person is acting beyond their powers or not in the best interest of dad then you must report this to the Office of the Public Guardian (this is the office that the LPA should already be registered with.
Here is how you can report any concerns:
https://www.gov.uk/report-concern-about-attorney-deputy-guardian