I am just posting this in the vague hope that it may be of use to someone else one day as I have found no other reference to this procedure anywhere online. This morning my iPhone4 was completely dead. Although I was thought it hadn’t needed charging I assumed that maybe I was wrong and it did, so plugged it into the charger. Nothing happened. The screen was blank, it wouldn’t switch on and a normal hard restart/reset of holding down the sleep/wake up and home buttons had no effect at all.
So I plugged it into my computer as I have known that kick an iPhone into life. Nothing happened to the phone screen. Still blank and no response. iTunes did however tell me that it couldn’t a connect to the iPhone as it received an invalid response. So life of some sort detected from the phone.
For some reason or another out of frustration I then tried quickly pressing the sleep/wake up and home buttons sumultaneously three times. This produced an instant response from the phone in that the Apple logo appeared, then after two or three minutes it synced with iTunes and then all settled down. As I thought it didn’t really need charging at it had over 50% charge left.
All a bit of a mystery but it now seems to be all working again.