A quick question in regards to claiming my inheritance please

Hi not sure how to word this, my solicitor made me aware in April this year that my inheritance that my decreased father left me was available to be claimed , I've not been able to claim it as I didn't have any identification, does anybody know how long they can/will hold on to it for?, I'm worried that if I don't claim it soon, that I might not be able to claim it at all, I have a provisional form signed and ready to be sent, I didn't get round to doing it due to circumstances, thank you in advance for your time.