A large number of Australians will be affected by the change.
A big change is coming for Australian-British and Australian-Irish dual citizens travelling to the UK.

Australian-British and Australian-Irish dual citizens will soon need to enter the UK using their British or Irish passports, after the UK government confirmed the rules would be "strictly enforced".
From February 25, dual citizens will no longer be able to obtain an Electronic Travel Authorisation (ETA) or a visa to enter the UK and may be refused boarding without the correct documentation, according to a Smartraveller warning.