HR question please

Hi - don’t know if right place to ask. Been asked to continue managing an employer under investigation. They have made allegations about a colleague. Unfortunately witnesses unfortunately have not corroborated their account.

I’m concerned about being subject of any false allegations while doing the 1-1’s. Are there any ACAS safeguards I can look at?

I’m thinking if things like meetings with door open, or in public spaces and Cc’ing manager after every 1-1 are acceptable ways to maintain transparency/ protect me and staff?

Thank you 🙏🏿