it was just in my pocket.
I took it out pushed the home button to bring the screen on to check the time and that was what greeted me on the screen.
I turned it off and back on again and it was fine.
A quick search on the net suggests if it has not genuinely overheated it has a dodgy sensor.
Apple will plug there diagnostic kit into it tomorrow and be able to tell me and hopefully give me a new phone.
I took it out pushed the home button to bring the screen on to check the time and that was what greeted me on the screen.
I turned it off and back on again and it was fine.
A quick search on the net suggests if it has not genuinely overheated it has a dodgy sensor.
Apple will plug there diagnostic kit into it tomorrow and be able to tell me and hopefully give me a new phone.