Got on my thruxton this morning and when i turned the key to 'on' the starter motor started turning over without having hit the starter toggle switch. So i turned the key back tried it again and same problem

. Note that the starter motor turns over with only the key turned to 'on', engine kill swith off an not having hit the starter toggle. So i got the bike started but could still hear the starter wurring away so shut the bike off. I am realy quite stumped where to even begin with troubleshooting this one. Anyone have any thougths? Greatly apprecieated. - thanks