The thing about Intervention Earth is, if you just listen to it, you’ll be like huh?? You NEED Enemy Lines afterwards because it gives it the whole and entire context of why any of IE is happening after. They are the same story and treating them as if you can have one without the other doesn’t work so well.
It’s not the jumping on point I’d suggest for a new Gallifrey listener. I think it probably can be listened to without knowing who Narvin is, but I think it’s richer for the context. It’s not the best ever story, but it does make sense really, it’s just asking you to trust it and keep going into Enemy Lines. I have a few issues with it, like Narvin’s characterisation is a bit wack and Omega might as well not be in it and it’s too long and a bit dull and okkk maybe it is kind of confusing but it isn’t completely makes no sense because the whole point of it is, it’s a what if? what if the worst happened? it’s like a dream, a nightmare. It’s the inevitable that Enemy Lines is trying to fight against.