Hmm, I think Clive the taxi driver is involved in the rape but I think there was a second person filming it on a mobile phone (hence the light Trish mentioned). Could it be Clive's stepson or even Ellie's son?
I assumed the light was from the taxi (with or without Clive actually performing the attack), but someone filming is a possibility too, and they've already speculated that Trish may not have been able to judge how far way the light was (i.e. a big light far away, or a small light close up).
That said, I've been pretty certain from the first episode that a second person was involved, if only in the clean-up afterwards. I've also suspected that it might be a woman, although it's difficult now to see how that would work. At this stage, the only female character I can see involved is the waitress Dana, and I doubt they'd throw such a minor figure into the frame at the last moment...