I think diabetics (particularly T2's) often just have poor glycemic control in general. Meaning poorer control of both lows and highs.
Many years ago when I was only pre-diabetic, my fasting levels would often be low like yours, but glucose tolerance tests showed much higher than normal spikes, indicating poor glycemic control in general. After my diabetes was "full blown" however they were always just too high.
If you're getting such low readings with any medication then I would say the the Newcastle diet has reversed your T2, at least back to pre-diabetes levels Jim.
Also, your levels might be so low because the Newcastle diet is a bit hypo caloric. If you're happy with your current weight then you might be better off with just a regular LCHF diet without calorie restriction.