Default [Q] Auto answering phone calls

Can anyone please suggest why my GT-N7000 has suddenly taken to answering incoming voice calls automatically without me having to do anything? I should know the phone inside out by now but I can't find the setting that controls this.

GT-N7000
Ultimate N7000 XXLT4 JellyBean 4.1.2v6
Kernel 3.0.31- 1103517

Thank in advance
Trevor