Currently only British and Irish Nationals and those with long term residence rights are allowed to arrive from Red List countries. Those without such rights, such as those using the Standard Visitor Visas, should be allowed to enter the UK, provided they undergo quarantine.
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Hotel quarantine has been effective in preventing importation of Coronavirus. We believe that nationality/residence status is an attribute with no epidemiological value and that the very real harms of a blanket ban on many travellers are easily avoided. The cost and inconvenience of hotel quarantine means that only those visitors with compelling reasons will still travel, and therefore numbers should not have a meaningful impact on capacity.