UK Emergency Alert Tests 2025

[4COR]

Even that level can be turned off, but it's a bit of a pain to find it in the phone.

Chances are they'll do a phone update on the morning of that Sunday which will sneakily turn it back on again...?

Who are "they"? Apple? Google? Samsung? <insert manufacturer>? Most core phone updates (as opposed to app updates) require human interaction - iPhones require confirmation, as do Google Pixel (Android) phones.

 

[Peter Mugridge]

Who are "they"? Apple? Google? Samsung? <insert manufacturer>? Most core phone updates (as opposed to app updates) require human interaction - iPhones require confirmation, as do Google Pixel (Android) phones.

Whoever issues the phone updates, presumably the manufacturers and system operators? Mine is currently a Vodafone VFD620 running Android Lite; it gets updates once a week, usually on Sundays, which are listed as coming from the app store and typically about 8 to 12 things are updated each week including the operating system and individual apps.

 

[jfollows]

It’s not Apple, Google and so on. They are constrained by the knowledge that they’ll lose 20% of the market if they do ( or whatever figure, but a significant one ).
No, it’s our government which gets to say “look how many people we alerted” which has to be 30% more than last time.
For the moment they don’t control the settings.

Governments don’t care about pissing off 20% of people, they only care about approval from 51% of people, it’s a different equation.

 

[4COR]

For those interested, a list of previous alerts is here:

Past alerts

A list of past emergency alerts that were sent in the UK

www.gov.uk

They include: severe flooding (including highly localised events), severe winds, and the movement of a WW2 bomb prior to detonation in Plymouth...

 

[43096]

I can't recall exactly what it was now but I do recall some people getting extremely het up when the first test happened a few years ago. There was a reasonable criticism that it could cause issues for people who have a hidden second phone (women suffering domestic violence was an example given) but most complaints seemed to trend towards the crackpot end of things!

Showing your age the nationwide system was discontinued around 1992(ish)!

Up here on the coast we got a siren test once a week at 10am on Tuesdays from the Wilton Industrial site (née ICI Wilton). Not sure if they still test as regularly anymore but it went off about a year or so ago as I was walking home from work (so presumably there was an actual incident of some description!) and it was during a period when Russia was really rattling the nuclear sabre which made for quite a sombre walk home even though there was no way it could be warning of nuclear strike.

We used to have the Broadmoor sirens round here which have been de-commissioned, but used to be tested every Monday morning - they were there to alert if a nutter had escaped from Broadmoor high-security hospital.

 

[sor]

I think it's fair to say that the UK version has not had the doom and gloom come to pass. People thought that because the US perhaps overuses its alert system that we would get the same, but for once the government has been very transparent as to how it will be used, and as shown above, they list every alert that has ever been sent and who (location) it was sent to. Not sure any other country goes that far.

 

[MrJeeves]

Even that level can be turned off, but it's a bit of a pain to find it in the phone.

Chances are they'll do a phone update on the morning of that Sunday which will sneakily turn it back on again...?

In all official and Google-certified Android builds, the highest level of CMAS alert (called "Presidential", after its initial introduction in the USA) is force-enabled. It cannot be disabled by an end-user whatsoever.

The Android source code highlights this:

// note that mPresidentialCheckBox does not use the startConfigServiceListener because
// the user is never allowed to change the preference
if (mAreaUpdateInfoCheckBox != null) {
    mAreaUpdateInfoCheckBox.setOnPreferenceChangeListener(startConfigServiceListener);
}

https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/apps/CellBroadcastReceiver/src/com/android/cellbroadcastreceiver/CellBroadcastSettings.java;l=513-517;drc=9eb7322f4b7585b2760a23f2425929ab66278bbe

 

[sor]

In all official and Google-certified Android builds, the highest level of CMAS alert (called "Presidential", after its initial introduction in the USA) is force-enabled. It cannot be disabled by an end-user whatsoever.

The Android source code highlights this:

// note that mPresidentialCheckBox does not use the startConfigServiceListener because
// the user is never allowed to change the preference
if (mAreaUpdateInfoCheckBox != null) {
    mAreaUpdateInfoCheckBox.setOnPreferenceChangeListener(startConfigServiceListener);
}

https://cs.android.com/android/platform/superproject/+/android-latest-release:packages/apps/CellBroadcastReceiver/src/com/android/cellbroadcastreceiver/CellBroadcastSettings.java;l=513-517;drc=9eb7322f4b7585b2760a23f2425929ab66278bbe

IIRC the UK doesn't use the "presidential" alert - this is why it can be disabled by the user. The government intentionally chose to allow an opt out, whether for the pub bore "I know when it'll rain!!!" type or if you're a victim of DV and you want to keep a phone hidden

I would presume it's level 3 in the ETSI spec - https://www.etsi.org/deliver/etsi_ts/102900_102999/102900/01.04.01_60/ts_102900v010401p.pdf - as phones will show it as a "severe alert"

 

[75A]

i'll be interested to see what happen on Sunday. I believe i've got it turned off on my Android Phone, Tablet & Laptop. Time will tell.
It would be blooming annoying if it does go off, I want to watch the British Superbikes in peace.

 

[MrJeeves]

IIRC the UK doesn't use the "presidential" alert - this is why it can be disabled by the user.

We don't use presidential alerts, but that doesn't magically mean you can disable them. They still exist. If a UK mobile network happened to transmit one, everyone would receive it. The point is whether the system is physically capable of sending an alert of this type.

My honest guess is that the option is probably there for something that really needs it, or it would only need a very slight change to use it.

The UK Severe Alert is the equivalent of EU-Alert Level 3. 2023's test used a message identifier of 4378 (dec), which 23.041-9.4.1.2.2 defines as EU-Alert Level 3.

TickTime : 520.921
Exy LTE RRC OTA Packet
 Direction : Downlink
bcch-dl-sch
 message -> c1 -> systemInformation
  criticalExtensions -> systemInformation-r8
   sib-TypeAndInfo
    [0] -> sib12-v920
     messageIdentifier-r9 : '00010001 00011010'B(4378)
     serialNumber-r9 : '01000000 00100000'B(16416)
     warningMessageSegmentType-r9 : notLastSegment
     warningMessageSegmentNumber-r9 : 0
     warningMessageSegment-r9 : '0454747A0E4ACF416110BD3C'H
     dataCodingScheme-r9 : '01'H (1)

Decimal	Hex	Meaning
4378	111A	CMAS CBS Message Identifier for CMAS Severe Alerts with Severity of Severe, Urgency of Expected, and Certainty of Likely. EU-Alert Level 3 Message Identifier for the local language as defined in ETSI TS 102 900 [32]. Korean Public Alert System (KPAS) Class 1 Message Identifier. Settable by MMI For subscriber opt-out requirements, see 3GPP TS 22.268 [28].

https://www.etsi.org/deliver/etsi_ts/123000_123099/123041/11.04.00_60/ts_123041v110400p.pdf

 

[Railwaycat]

i'll be interested to see what happen on Sunday. I believe i've got it turned off on my Android Phone, Tablet & Laptop. Time will tell.
It would be blooming annoying if it does go off, I want to watch the British Superbikes in peace.

Have you thought about just switching your phone off?

What is so important that people leave their phones on 24/7? Has nobody got a landline?

 

[Bletchleyite]

Has nobody got a landline?

What would I want a landline for?

 

[4COR]

What would I want a landline for?

To get scam phone calls? (That was pretty much all that came through ours until we got rid of it...)

 

[Bletchleyite]

To get scam phone calls? (That was pretty much all that came through ours until we got rid of it...)

That's exactly why I got rid!

 

[Peterthegreat]

That's exactly why I got rid!

Me too.

 

[75A]

My Mobile is on 24/7 because it might safe my life.
I'm Diabetic and an App on my phone is linked to a patch on my arm by Bluetooth, that sounds an alarm if my Blood/Sugar is out of range.

 

[J663738]

I would love to be in a cinema at 3pm on Sunday, all though in my recent experience it probably wouldn't be much different to the last time I went!

 

[Jimini]

I think it's fair to say that the UK version has not had the doom and gloom come to pass. People thought that because the US perhaps overuses its alert system that we would get the same, but for once the government has been very transparent as to how it will be used, and as shown above, they list every alert that has ever been sent and who (location) it was sent to. Not sure any other country goes that far.

Yep -- I got one on my work cell phone mobile earlier today about a convicted paedophile who has moved from a correctional facility up-state to Randall's Island in NYC. Probably get 2-3 alerts per week.

 

[Bletchleyite]

I would love to be in a cinema at 3pm on Sunday, all though in my recent experience it probably wouldn't be much different to the last time I went!

I've actually had to ask people to stop scrolling TikTok videos out loud in a cinema. I know some people would debate whether it's OK to do it on a train or not, but I don't think there is any possible argument for it being OK in a cinema!

 

[greatkingrat]

I would love to be in a cinema at 3pm on Sunday, all though in my recent experience it probably wouldn't be much different to the last time I went!

I see they have carefully chosen a day with no major football matches. That's a shame, as 50000 sirens going off simultaneously would be fun!

 

[OscarH]

Yep -- I got one on my work cell phone mobile earlier today about a convicted paedophile who has moved from a correctional facility up-state to Randall's Island in NYC. Probably get 2-3 alerts per week.

Yeah, this is taking the mick. The UK government so far seems pretty sensible at drawing the line, long may it continue

 

[GusB]

I've got three "toggles" in my phone's "Emergency Alerts" settings:

• Allow alerts (switches everything on and off)
• Extreme alerts (disabling this also switches off severe alerts)
• Severe alerts

I'd question the wording, though; to me there isn't much difference between "extreme threat to life and property" and "severe threat to life and property".

 

[styles]

I'll be driving at the time.

So I've disabled the alerts until next week.

For anybody wanting to do the same: https://www.gov.uk/alerts/opting-out

iPhone
To opt out:

Go to your settings and select the ‘notifications’ menu.
Scroll to the bottom.
Turn off ‘severe alerts’ and ‘extreme alerts’.
Android phones
To opt out:

Search your settings for ‘emergency alerts’.
Turn off ‘severe alerts’ and ‘extreme alerts’.

I'll switch them back on next week.

 

[JamesT]

I see they have carefully chosen a day with no major football matches. That's a shame, as 50000 sirens going off simultaneously would be fun!

Not quite to the same scale, but there will be the NZ vs. Ireland women's rugby match then. I wonder if the TV coverage will pick up a stadium full of phones going off.

 

[sprunt]

is there a conspiracy theory associated with this system? I dot like to miss the latest crack pot "thinking"!

Shortly before the last test a couple of years ago i got talking to someone looking at the same view as me when I was out walking, and apropos nothing he asked me if I had the alerts on my phone switched off. I said that I had, and he said "Good, because if that alert gets to your phone it will allow the government to see the details of all your bank accounts."

There's also this bit of nonsense:

It’s not Apple, Google and so on. They are constrained by the knowledge that they’ll lose 20% of the market if they do ( or whatever figure, but a significant one ).
No, it’s our government which gets to say “look how many people we alerted” which has to be 30% more than last time.
For the moment they don’t control the settings.

 

[MrJeeves]

For those who don't know, the nature of Cell Broadcast means that there is no information held about how many devices have received an alert. It is quite literally impossible to know how many devices have received an alert.

It is broadcasted like TV or radio in the sense that your phone doesn't reply "yes I have received the alert" in the same way your set top box or a radio doesn't reply to the transmitter or satellite to say "I am now watching BBC Two"*.

The mast simply starts saying "I am now broadcasting a message, please look for the data every 512 milliseconds" and any connected devices will then piece together the message out of tens of fragments, then display it to the user.

* though if your box is connected up to the internet, it might volunteer that information anyway for viewship statistics

 

[Snow1964]

Got one in Rotterdam, when a massive fire in a dockside warehouse about half mile away was throwing out huge amounts of toxic black smoke. The Guide on our tram (heritage tram route 10) told us what it said (the warning was obviously in Dutch)

So now have the original test message (in English and Welsh), and one in Dutch. Now looks like Sunday will be third message.

 

[J663738]

It is broadcasted like TV or radio in the sense that your phone doesn't reply "yes I have received the alert" in the same way your set top box or a radio doesn't reply to the transmitter or satellite to say "I am now watching BBC Two"*.

* though if your box is connected up to the internet, it might volunteer that information anyway for viewship statistics

I don't think this is entirely true, the base station would have a list of currently connected devices, so would know which phone and subscribers got the alerts, how else would the number of alerts be otherwise calculated?

Also most internet connected smart TVs now do log what you are watching unless, you go into the menus and opt out.
In France STB's do have an RF revertive back to the transmitter, via the TV Antenna.

 

[MrJeeves]

I don't think this is entirely true, the base station would have a list of currently connected devices, so would know which phone and subscribers got the alerts, how else would the number of alerts be otherwise calculated?

A device doesn't need to be connected to the base station to receive the alert. It just needs to observe the base station's broadcast messages. A device with receive-only capabilities would even be able to show it, if one existed (or if someone managed to break the Tx path of the radio).

The message is broadcast through the System Information Blocks (SIBs) in 4G/5G, which are multicast messages that broadcast to anyone that happens to be listening, rather than to specific devices.

 

[OscarH]

The mast simply starts saying "I am now broadcasting a message, please look for the data every 512 milliseconds"

Is this a realistic time period, segments every 512ms feels slow