How to handle unavailable information for Tax Return

How to handle unavailable information for Tax Return About a year ago, I received a lump sum inheritance from the estate of a family member. In the lead up to receive the disbursement, the solicitor managing the distribution of the estate asserted that IHT had already been paid, but that the sum may have accrued interest income, which I then need to declare and pay income tax on. I'm familiar with this process from a previous family member's estate (I'm at the "all your grandparents are dying now" age :( ), and in that case the relevant solicitor provided an R185 form detailing the amount of interest income accrued, and the amount of tax already paid. However, this solicitor never provided me an R185, and (since the estate has now been fully distributed, and the account closed) is no longer responding to emails. So I have no way to determine how much (if any) interest the inheritance sum accrued. I'm now filling in my Tax Return for 2025-25, and should be including the relevant number in that Return. But I can't. Because I don't know the number and don't have any means by which to determine it. What do I do?