Warning About Device Being Accessed from another Location
Periodically I get a message saying words to the effect 'a device is being used in a location near London, do you wish to allow this device access' and then when I change my ID the same message comes up when I try to log in to my devices (I use one to authorise the others). I live 600 miles from London and have no devices there. Is it possible one of my devices thinks it is in London (yet knows its not...) or could someone somehow be filtering all my devices via another device in London? If so, how do I stop this? I've changed my ID 3 times but the same message keeps coming up and if I prevent access, I can't use my other devices (laptop, etc). Thank you for any help.
iMac (27-inch, Late 2013), OS X Mavericks (10.9.1)