I was watching a National Theatre Live viewing yesterday during the time of the alarm. The theatre had asked us to turn off our phones and I did. I was interested to hear the sound of the alarm but was sure that someone would leave their phone on anyway. Sure enough, the alarm sounded on one phone at 3pm and then on another at 3.05. I heard an explanation of why the timing was variable on the radio, this morning. However, it is just as well that this test took place as it seems that it was not universally successful. Lessons, as they say, will have been learned.