Who to put as referee?

[YBR]

I have worked in the same company for 15 years but am looking to move.
My current line manager has been in the job since January and is leaving within a month. My previous line manger knows me better and I have his permission to use him as a referee. Which should I use?

I know it will look odd if I don't put my current line manager down, or if he has left by the time they ask for the reference. So I'm thinking I could put both down with a brief explanation. Could there be any issue with that?

I'd go with the one who knows you best. Make sure in reference its clear this is the case

You can put whoever you want down as a reference. A future employer will contact your HR team (if there is one) for a work reference which will probably just confirm when you worked there and I don’t think anyone really cares about personal references whether it’s from an ex-colleague/manager or your mother.