You can do this by a declaration of trust. You will need a solicitor to draft it for you. Let me know if you need further assistance on this.
Thank you for your question
My name is ***** ***** I have been a family lawyer for more than 30 years.
Your ex is likely to be worried about a claim within the financial side of divorce proceedings which is NOT covered by a Declaration of Trust.
When was the divorce and what agreement - if any was reached on the finances at that time?
As a property lawyer I have drafted many declarations of trust for may different situations. I would be happy to assist you further if necessary. Please do let me know if you have any further questions.