How much would it cost to install one electrical socket?

[TennesseeDays]

We are in rented acommodation, so would have to ask landlord's permission, but how much would it cost to fit one double electrical socket into a wall? There is one in the adjoining room, on the other side of the wall to the place where we want the socket, so the wiring is presumably there already.
If we can't get one fitted, we will have to run an extension lead across a doorway, which is obviously a massive pita.
It's an old house, probably a bit over 100 years old if that makes a difference.

I'd have thought it was something the landlord would have to sort themselves rather than you do it with their permission. So they might not have any desire to keep the costs down. I would guess at £100-150. It can be more of a pain than you think, and might need some plastering work and redecorating doing too.

I would go along with the previous post on this. Being an older property plaster etc
coming off a possibility (this happened to us) This really is a landlord job. One thing which is handy: new socket covers now come with a UBS portal/connection which is great if you are short of sockets so you can run computers/apps etc from it thus freeing up your sockets for other things .Firm called Tlc do them and you could offer to pay for it (not expensive)

The only way as a landlord I would countenance this is if you got a quote from a fully qualified electrician and paid for the new Electrical Compliance Certificate (I think that is what it is called) cost around £150 then I'd be fine with it.