I realize the article was about the UK, but this entire encryption/spying issue certainly applies to the US as well. My comments are regarding the US because I don't know enough about the UK's laws and general situation to speak on it.
The cat is out of the bag. End to end encryption that is very easy for the average user to use exists. There's no going back. These terrorists that they are so worried about are going to use it (if they have any common sense), even if it is outlawed somehow. Making it illegal or extremely difficult to use is the same as gun control - the criminals are still going to break the law because their end goal is a crime far worse and if they are willing to commit that crime then they are surely willing to commit the lesser crime of not getting a license for a weapon or possibly using end-to-end encryption.
In the US we supposedly have the 4th amendment to protect against this NSA spying criminality. The 4th amendment protects against both search and seizure. The giant dragnet they use to sweep up all communications over private channels is supposed to be a crime without a warrant. And when done in bulk it should be easily considered a mass, rank violation of the 4th amendment. For example, in the case of your cell phone, you agree to allow a private business to forward your data and communications. They theoretically can access it all, including your GPS because of the cell tower triangulation. That should be understood as necessary to providing the base service. But your agreement is only with the telecom provider, not the government. The government just decided to stick it's head in and declare itself to have a national security interest in the data of not just you, but everyone in the entire nation, and demanded access to it all.
What's worse is that these programs have not been proven to actually stop terrorists:
https://theintercept.com/2015/11/17/u-s-mass-surveillance-ha...
http://www.nbcnews.com/news/other/nsa-program-stopped-no-ter...
In fact, based on my memory, every instance of a thwarted attack has been the FBI actually communicating directly with alleged terrorists using undercover agents. This is how actual investigative work has historically been done. They followed up on tips, evidence, etc. and followed the leads and performed a real investigation and followed the proper warrant protocols. And doing it "the hard way" has yielded them more terrorists in handcuffs than the NSA.
The results are so abysmal for the PRISM program and it's siblings, that it begs the question whether or not stopping terrorists is even the real purpose. Personally, I have never thought it was the main goal. Sure, they might catch some, but I think the real purpose is to make sure no one poses a political threat. If anyone starts to get out of line or cause too many problems, they can just rifle through all their data they have on you and find something to use against you. How many people are clean enough to escape that? Ever, even once, downloaded an illegal mp3? Ever watch a movie on an illegal, streaming tube site or use torrents? Ever cheated, even a little on your taxes? Ever cheated on your spouse? Have a porn fetish that others may find unsavory? In the closet? Are you fully in compliance with every housing regulation? Have permits for every little thing that legally requires a permit? Have any secrets that aren't illegal but may be embarrassing? Done anything that isn't illegal but people would look upon with disdain? It might just be used against you.