Something I finally worked out

I was re-watching Doctor Who: "The Unquiet Dead" earlier this week.  I had always wondered how the Gelth knew about the Time War, which they used to manipulate the Doctor into helping them.  During this latest re-watch I realized, they exploited Gwyneth's gift, her "sight" during the seance to do this.  When I recalled her earlier conversation with Rose, how she'd seen where Rose had been and was still yet to go to, that's when it dawned on me.