United Kingdom Electronic Visa Waiver

 An electronic visa waiver has been introduced for entry into the United Kingdom and Northern Ireland, expediting the arrival process for citizens of select Persian Gulf countries (including Bahrain, Kuwait, Oman, and the United Arab Emirates). 

Those nationalities that are already exempt from requiring a visa for the UK and Northern Ireland are not obligated to apply for this waiver.

 https://www.gov.uk/government/organisations/uk-visas-and-immigration