Mobile networks in particular have been put under pressure as people use their phones to contact friends and family following the explosions.
Luckily, I was 10 minutes late leaving home otherwise I could very well have been on that first train which was attacked near Aldgate. When the Central Line shut down, I tried to get a bus, and when all the bus service into central London was shut down I gave up and started walking home. I suspected that the rumours of terrorist attack were true. All this while I was trying unsuccessfully to use my mobile to ring the office. Finally, I decided to try sending a text message and this worked. Text messages normally are delivered virtually instantaneously and there is a time stamp indicating when the message was sent. During the morning and early afternoon of Thursday, I was receiving text messages that had been sent between 20 minutes and one hour previous. Some of the problems on the mobile networks were the result of a protocol to reserve mobile capabilities for the emergency services. The police have the authority to switch cells to emergency service and then people with specially registered SIM cards in their mobile can take priority. Presumably, some amount of capacity is also held in reserve for these people as well. I had moved the weekend before and my landline was not yet installed. Also, I live near a large hospital. I noticed that my mobile didn't function at all even late on Thursday unless I left home and travelled a kilometer or two from the hospital. Presumably, the cells in this suburban location had also been switched to emergency service. --Michael Dillon