My tortoise has started biting, please help!

[LittleMac]

My 4 year old marginated tortoise has started biting. It's been over the last year or so but at first it was like a little nibble, now every time my feet or hands are in his eyesight he runs towards me (or anyone for that matter) and bites very aggressively. It's very painful and quite upsetting because I want to be able to be around him without getting attacked. Has anyone had this problem before and had any success with discouraging it? Any advise would be really appreciated, I'll try anything!