Can anyone tell me what this is?!

[Sam odell]

Socket on wall, thought it was aerial, but looks like it may have live power? And socket is not round, it has a crescent wedge in it, can't imagine what it's for or how to get rid of it? 

[ProDave]

Flex outlet plate, would typically be used for a heater or similar in a bathroom and the power switched from a switch on the wall outside the room.

[Sam odell]

Many thanks. So it's live and dangerous etc and I need an electrician to remove it.? 

[BotusBuild]

If you're not happy doing it yourself, yes, get an electrician 

[Mr Punter]

There should be a switch somewhere nearby but you will need a sparky.  Your wiring looks old and may not have the same level of protection as more up-to-date installs.