Thanks for your help I am sorry if I cam across a bit dumb I was not implying that it just cracked on its own more to the point that it's a fault ie the phone overheating causing excessive thermal movement in the screen and the cracks from such issues or maybe just cracking from the phone flexing in a pocket both of which would be a faulty phone under the consumer act a item should be fit for purpose and if it is the case it's not fit for purpose then the guarantee is immaterial as there is a responsibility.
Jim