What is end to end encryption and why are police concerned about its rise?

End to end encrypted apps have become increasingly popular in last 10 years with billions of people using them every day.

But as Meta plans to roll it out on apps like Messenger and Instagram, governments around the world are increasingly worried.

Without the ability to read any of the messages sent, police say they will find it harder to catch and convict criminals including terrorists and child abusers.

So what is end to end encryption and how does it work?

Cyber Correspondent Joe Tidy explains.