Sudden change in Behaviour

Question
Over the last few days only, I've seen a dramatic change in my gelding's behaviour.  He's six years old and has been doing great, he's got a lovely, willing attitude to schooling and always tries his hardest. However, out of the blue he bolted with me in the school, and the worst thing was he became very hard to stop.  I find this puzzling as he's never done anything like it and usually has a lovely, sensitive mouth, and is extremely obedient to my aids.   I took him in the school again the day after, and out of the blue, from walk, he did it again, looking very anxious and worried.

 He has shear mouth, and is due for his 6 monthly teeth check next month.  There has been no change in tack, diet or routine.

Your help would be very much appreciated,
Thank you


Answer
There are several things I would check if I were you. I would check his eyes first to make sure he is not experiencing a vision problem. If he is having vision problems he might bolt because he can not see things clearly. If that turns out ok the next thing I would do is have his teeth done now. Are there are new horses, buildings, dogs, ETC that are now in the area?