It has been since 2013 that an official report, published by the GSMA (the consortium of all GSM mobile operators worldwide) clearly stated that there is no need to introduce the compulsory registration of the identity of the owners of mobile phones or SIM cards, as a way to simplify the investigatory process in any crime.
“The compulsory registration of ownership of mobile telephones would not deliver any significant new benefits to the investigatory process ..."
In other words, "burners", anonymous "SIM" cards, "SIM" cards under someone else name, all those are as anonymous as our business card!
Yet, a good percentage of questions we receive on Quora keep asking the same question: is it more anonymous if I use a burner or an anonymous SIM card? The answer is always the same. No. Using an anonymous SIM card or a burner does not increase the level of privacy of the user. Have a look at the video in the NEWS section on this page, to understand why.
In force of the current UK international agreements, and according to the UK Investigatory Power Bill 143, any telecommunication company located in the following countries can be sued by the UK Secretary of State
"to enforce a technical capability notice which relates to only interception warrants or an authorisation or notice given under Part 3."
"The obligations that may be specified in regulations under this section include, among other things--"