"I have difficulty in seeing the double N."
So do I, but it's an expectable trouble (sometimes I write them so recklessly myself), while any other name I can think of simply does not fit. It must be
Joannes.
BTW, are you used to this style of handwriting? Is it what gives you trouble recognising the name? Because I had no trouble recognising it as
Joannes; I'm Czech and we still write almost like that. It's quite clear writing, I've seen much worse...