You cannot use a jammer of any kind in the United States, for almost all values of you, including state and federal penal agencies. https://www.fcc.gov/general/jammer-enforcement

That's an interesting US fact, but the story is about the UK. Is it likewise restricted there?

The law was changed to permit jamming in prisons. It is quite difficult to implement because you have to avoid jamming outside the prison, but a successful feasibility study was carried out. And the government decided it was too expensive to roll out nationally.

Yes, it is.

https://www.ofcom.org.uk/spectrum/interference-enforcement/s...

Criminal, according to Ofcom regulations.

https://www.ofcom.org.uk/spectrum/interference-enforcement/s...

There are after all good reasons to ban them, but even if those reasons didn’t exist, the Tories would ban them for their usual “law and order” reasons.

As an alternative it'd be nice to see some higher-tech GSM detection technology that allowed them to pinpoint the phones (or at least be aware of their presence).

So, cell towers?

I don't know a tremendous amount about cell towers, but I was under the impression that they couldn't very accurately pinpoint locations - I was thinking more of a [foxhunting](https://en.wikipedia.org/wiki/Transmitter_hunting)-style location, where you could (hopefully) find a phone's hiding place with relative ease.

A recent article on how to track cell phone: https://news.ycombinator.com/item?id=14803443

I guess they could use a "stingray" type device, which could be used to control, rather than interrupt the cell signal.

Rectal exams.

Lead paint? :)

- Just kidding...

Faraday prison cells.

or just a faraday cage.

Why kidding? That should work. Paintings with metals is really a thing.

Lead is toxic to human, any other metal can do.

I suspect any quantity of metal sufficient to act as an RF shield or Faraday cage would be toxic to humans in paint form.

Unless ingested, iron should be fine. It is also low maintenance.