A degree in the subject that requires a similar skill would be good enough for me. I have a degree in Philsopshy (non of it religious) and teaches RE. A lot of the subject knowledge you can learn on the job particularly up to GCSE level. A level a little more tricky I teach Philosophy and Ethics beacuse it is obviously more of a strenght than say Hinduism and with everything you get better the more you do it. For me a good teacher counts for a lot and when interviewing the answers to "Why teach RE?" and "What do yo uthink RE is all about?" are far more important than what degree you have. I have had trainees with theology degrees teach awful RE lessons and a teacher who specialises in another subject who teaches amazing RE lessons. For me RE is all about the WHY? not the WHAT? I think it is more difficult to draw out the why than teach the what!