Two Lights. One Switch

[richie4236]

In our hallway we have a double switch. One switch operates the lights in the hall, and the light outside the front door. The other does nothing at all. I'd like to change it so one does the internal lights and the other does the outside light. I assume that's how it's supposed to be wired, and I have no idea why the previous owner of the house would have changed it - but is seems he did.
I've attached a picture of the wiring. There's only one switch on this circuit. Is it something I can change easily, or should I get an electrician in to do it? Thanks.

 

[Doggit]

Am I right in thinking there's a second light switch in the hall, either at the other end, or upstairs. The blue and yellow wires suggest it's a 2 way system. The other red and black wires should switch on another light somewhere, so it's possible that they've taken the wires from the hall light to the outside light. I think you're going to need an electrician on this one.

 

[Echo the husky]

Are you saying the outside light comes on with the hall light?

Is there a second light switch somewhere else that controls the hall light?

 

[securespark]

Electrical porn!

Where's the video??

 

[securespark]

It sounds like the porch light is linked to the hall light (the one with r&b wires??).

The other is a 2 way. Is it for the landing?

 

[EFLImpudence]

He said one of them did nothing. We don't know which is which.