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Can I summarise the facts please?
The transfer the property into your sister’s name because your sister lent you £200,000?
Your sister said that once that was repaid, she would transfer the property back?
Now she wont.
Is that a summary?
Who dealt with the transfer of the property from your mother’s sister? Solicitors?
Has £200,000 been repaid and how if your sister not accepting it? Can your mother simply put it into her bank account?
What proof is there that the house will be transferred back on the payment of £200,000?