Hope this helps...
It doesn't start on G but on F. You have to look at the first letter of every word.Father - F, with one flat on BCharles - C, with no accidental (you could see it as adding a sharp on the B flat)Goes - G, one sharp on FDown - D, and so onAnd - AEnds - EBattle - BSo obviously the sharp key signatures (C#, F#) are not covered in this sentence.
The G was the key in which the F occurs. The pattern was clear going down the page. (at least to me it is).