Thanks for your question. It's a difficult situation and you have my sympathies.
There is no requirement for a Will to be lodged somewhere specific, it's would have been the choice of your father where he left it. If he used solicitors during his lifetime then I would certainly give them a call and let them know the situation and that you need to find out if he has lodged his Will with them.
If he has made a Will then it will specify who he wished his executors to be and the solicitors will get in touch with them (if you are not named as executors yourselves) and refer the matter to them urgently.
A person can lodge their Will at the probate registry and you can check to see if they will confirm if they have it lodged but you will have to explain your situation to them. This is not a requirement and it is fairly uncommon to have it lodged in this way - most people either leave it with their solicitors or retain wills themselves:-
If the estate is small (eg. less than £5000.00) then a grant of probate may not be required and the estate could be administered with a grant. If the estate is much more than this then a grant of probate will be required. If this is the case then you should make a "standing search" of the calender, which will notify you and send you a copy of the grant if one is take out within 6 months of the date of the search:-
If you have real concerns about your sister then you and your other sisters need to get immediate specific advice from a local solicitor who will write to your other sister and explain your concerns, it may be that this becomes a case of contentious probate or it may prompt her compliance. You should also call the banks and tell them of your concerns.
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