- European Commission in the UK - https://blogs.ec.europa.eu/ECintheUK -

Eurocrats change traditional road numbers

“No more M4 as AA puts E-numbers on the map – Revised road atlas goes Continental to fall in line with Brussels system” (Daily Mail, 24 September 2001, page 34)
The AA has decided to broaden the horizons of the motorway network by ‘going European’. …the road from London to South Wales is no longer the M4. It has been reclassified as a 150-mile section of the E30 running from Cork to…Moscow. The new classifications are part of the Trans-European Road Network, an idea dreamed up in Brussels.

The European Union is not going to introduce an EU road numbering system.
In 1975, the United Nations decided to give major roads standard numbers to make navigation easier for long distance travellers. This has nothing to do with the EU. The EU’s Trans-European Networks project, which is improving transport links across Europe, will continue to use these numbers rather than create confusion with a new system. The UK will carry on classifying its roads as it wishes.