Every now and then, or maybe never. It is done by OfCom, and the current classification dating from December 2010 seemed (IIRC) to imply that it was the final revision. Which if I'm right, would be daft.
Like their rule about 5 days maximum for a MAC, which still applies but is not enforced

. Or the ASA accepting that "unlimited" means "whatever limit or restriction the ISP chooses to apply".
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