Which newspaper is not signed up to the IPSO?

The Guardian is the correct answer because it is not a member of the Independent Press Standards Organisation (IPSO), which was established in 2014 to oversee the conduct of the press in the UK and ensure ethical journalism.

The Guardian is instead a member of the Independent Press Complaints Commission (IPCC), which is an alternative body that deals with press complaints and ethical standards. This distinction is significant as it highlights differences in how various newspapers choose to regulate their standards and handle complaints from the public, influencing their editorial policies and accountability.

In contrast, The Times, The Sun, and The Telegraph are all signatories to IPSO, which means they have agreed to adhere to its code of conduct and accept its processes for resolving complaints. Understanding the affiliations of these newspapers with respective regulatory bodies helps in analyzing their commitment to editorial standards and the implications for press freedom and accountability in the media landscape.