First of all, thanks for all of the replies, and apologies if I wasn't clear in my original post. This is new to me, so I'm probably not using the correct terms, and maybe I'm making wrong assumptions.
The situation is that my neighbour's house now has five security cameras fitted, and they are linked to his upstairs TV. The cameras' leads (they are wired, not wireless) all go through the attic, and meet and go down into his bedroom, and are connected to the camera's hub box (or whatever it's called, the unit that houses the hard drive and everything). The hub box is wired into his bedroom TV, and everything is working fine, he can view the cameras on the TV, there's no problems with the security system at all.
The problem is, he wants to connect the camera hub box to the internet, so it can email him if say he's at work and one of the camera's detects moving in his yard (he has lots of valuable fish, some of them are *massive*). He doesn't want or need to view the security cameras on the downstairs TV, just for the security camera hub box (which is upstairs) to communicate with the internet, via the house router, which is downstairs. Ideally, he doesn't want to loop a cable all the way from the bedroom to the router (from the camera hub box in his bedroom, down to the router in his living room), or to drill a cable though the bedroom floor (for the cable from the camera hub box to the router in his living room) if he can avoid using a long cable.
The router is SKY broadband, which wirelessly connects to the usual stuff (tablet, phone, an Amazon Fire stick type thing). Everything is working with that router, but he has a second router (identical to the first) that isn't being used for anything, and he was hoping that he could somehow introduce the second, previously unused router into the equation, and get the two routers working together, meaning that his camera hub box would be connected by a short cable to a router (call it router two, the new router that would be in the bedroom next to the camera hub box) and that router two would communicate wirelessly with router one (the downstairs router, the one that's connected to the phone line and feeds everything else, i.e. his tablet, mobile phone, etc).
Is this possible, or does it require a different item (not a router) to be connected to the camera hub in place of router two? Please don't assume I know anything about this (I pretty much don't), it's all new to me.