There is an agreement between the European Union and the United Kingdom on a new cooperation from 1 January 2021. What does that mean for you as a traveller?
As EU-citizen, you can travel to the United Kingdom with your identity card until 30 September 2021. From 1 October 2021, a passport will be compulsory. A visa is not required when travelling to the UK for stays shorter than 6 months. British Nationals can no longer use the e-gates at border controls. You can find more information on the website of Foreign Affairs.
You will have to declare cash and valuables at customs, and the quantities of alcohol and cigarettes you can bring are lower, more information can be found here.