What's wrong with my lawnmower?

[Carruthers]

I have a Toro 20956 lawn mower which won't start.
I've charged the battery but using the key to start it results in absolutely nothing happening, no sign of life whatsoever.
Attempting to start it by pulling the recoil start handle doesn't produce any sign of life either.
A couple of points. I left a small amount of fuel in the tank at the end of the mowing season in October last year but I've filled the tank with fresh fuel so I don't think that the problem has its roots there.
Secondly, in May last year I had trouble starting it and replaced the spark plug.
This model has a well known weak point in the factory fitted plug which was, I think, by Bosch. I fitted an NGK plug and it started straight away.
I removed the plug a few days ago and it wasn't oiled up and appeared almost as good as new.
I'm really puzzled by this and, although I have an old electric mower, it's a pain managing thirty yards or more of mains cable.
I am acutely aware of the possibility of slicing through the cable as I once managed to do that with a hedge trimmer and narrowly avoided 240v up the Carruthers left arm..
If anyone can offer advice, preferably of a constructive nature, I'd pleased to hear from you.

Thanks, Dwellars