Mobile Phone Networks Access Overload Control in the aftermath of the July 7th 2005 terrorist attacks in London

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It has now emerged why there were conflicting reports about the state of the mobile phone network last July 7th 2005, in the aftermath of the terorist bomb attacks in London:

Report of the 7 July Review Committee (.pdf) of the Greater London Assembly.

"London's telephone networks experienced unprecedented volumes of traffic. Vodafone experienced a 250 per cent increase in the volume of calls and a doubling of the volume of text messages. There were twice as many calls on the BT network as would normally be the case on a Thursday morning. Cable & Wireless handled ten times as many calls as usual to the Vodafone and O2 networks - 300,000 calls were placed every 15 minutes, compared to 30,000 on a normal working day. O2 would normally expect to handle 7 million calls per day. On 7 July, 11 million calls were connected - 60 per cent more than usual - and this does not include unsuccessful calls."

This was all entirely predictable, given the experiences of New York on Spetember 11th 2001, and the large scale electrical power outage of 28th August 2003 in South London

However, there is is only so much a mobile phone network operator can do to temporarily and marginally increase their network capacity in an Emergency e.g. "call gapping" to arbitrarily prevent a percentage of dialed calls from actually connecting, (which doubles the radio capactiy at a Cell Base Station, but results in lower call quality) and perhaps , turning off the Handset to Cell Base Station Encryption etc. Since none of their "critical national infrastructure" was actually out of action as a direct result of the terrorist bombs, it appears that the mobile phone network operators' emergency plans did not kick in immediately, as they expected their networks to cope ok.

What is not acceptable is the apparent lack of coordination between the Metropolitan Police "Gold Command" who were nominally in charge of the emergency, and the City of London Police (presumably one of the "Silver Commands"), who for their own understandable reasons got the O2 mobile phone network to implent Access Overload Control (ACCOLC) , in an area of about 1 kilometer around Aldgate Tube station i.e. covering much of the City of London, in spite of the decision by Gold Command not to impose ACCOLC in the same area at the request of the London Ambulance Service.

Apparently the Emergency plan does not require the mobile network operator to seek confirmation from Gold Command for initiating ACCOLC,

What is the point of having a Gold / Silver / Bronze" emergency incident command and control structure if it is not actually in command ?

It also emerged that nobody appears to be sure how many key emergency workers are actually carrying mobile phones equipped with the specially issued SIM cards, which would allow their phones to work, when the general public is excluded from the network under ACCOLC.

  • "3.10 A system exists to restrict mobile phone network access to the emergency services within a specified area. This system, called the Access Overload Control (ACCOLC) is seen very much as a last resort. It is expensive to implement and can cause public distress or panic. The decision to activate ACCOLC can therefore be taken only at the highest level of command: the Gold Coordinating Group.

    3.11 We asked representatives from the emergency and transport services whether ACCOLC had been activated anywhere in London on 7 July. We were told that the first meeting of the Gold Coordinating Group, at 10.30 am, considered whether to close down mobile phone networks to the public at any of the sites where the emergency rescue effort was being mounted. The London Ambulance Service told us that problems with mobile telephones and radios led them to as the Gold Coordinating Group to activate ACCOLC in the area around Aldgate station, and that their request had been refused by the Gold Coordinating Group. It was decided that ACCOLC should not be activated, because of the risk of public panic and also because it was not clear that the right personnel would be carrying ACCOLC-enabled telephones.(28) If they were not carrying this equipment ACCOLC could have made matters worse. As it was, at least some mobile telephone calls were getting through some of the time. Had ACCOLC been activated, key personnel who were not carrying specially-enabled telephones would not have been able to make or receive any calls. This is clearly a major flaw in the system: there is no point in having the technology to enable key people to communicate with each other if the relevant authorities do not make sure that the right people are in possession of that technology.

    We subsequently found out that in fact ACCOLC had been activated, by the City of London Police, on the O2 network in a 1km area around Aldgate station. This was in response to the fact that the City of London Police were experiencing serious communications difficulties in the area, and this was hampering their response.Despite the Gold Coordinating Group decision, the City of London Police made a request at 12 noon to O2 to shut down the O2 network to the public in a 1km area around Aldgate station. O2 carried out the appropriate validation procedures, but these procedures, set by the Cabinet Office, do not include verifying the request with the Gold Coordinating Group. The O2 network was therefore closed to the public - outside the command and control structure - at about noon, and remained closed that period of time, O2 estimates that 'Several hundred thousand, possibly maybe even more than a million' attempted calls by members of the public were lost.(29)

    James Hart, Commissioner of the City of London Police, explained to us in writing, in February 2006, how and why the decision was taken, outside the command and control structure, to instruct O2 to shut down its network to the public. He told us that the senior officer in the Command and Control room 'witnessed a gradual deterioration of his ability to communicate with operational officers at the scene via the mobile phone system'.


  • It also appears that the public advice not to use the mobile phone networks unless absolutely ncessary was lost in the inadequate media briefings given by the Metroplitan Police that day. They naturally tended to focus only on Police aspects of the situation and not the wider Emergency ones, which is understandable, but not acceptable, in their role as "Gold Command".

    Sir Ian Blair's statements also tended to overshadow the briefings given by less senior officiers, which were not as widely reported by the broadcast media, resulting in out of date information being re-broadcast hour after hour.


    Some of the failings identified in the report are just shocking.

    How many people reading the report will share my astonishment that the Emergency Response Unit - who work almost wholly undergorund - lack radios which will operate below surface or that this vital rescue service lacks blue light service?

    @ Martin - yes we noticed that, and the fact that they get Congestion Charged !

    >> yes we noticed that, and the fact that they get Congestion Charged !

    I know - an essential public service has been paying public money to a toll scheme from which a private company derives a profit.

    If it wasn't such an important issue it would be laughable.

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