The Foreign Secretary Boris Johnson has today held conversations with the US government and as a result we can clarify that:
the Presidential executive order only applies to individuals travelling from one of the 7 named countries
if you are travelling to the US from anywhere other than one of those countries (for instance, the UK) the executive order does not apply to you and you will experience no extra checks regardless of your nationality or your place of birth
if you are a UK national who happens to be travelling from one of those countries to the US, then the order does not apply to you – even if you were born in one of those countries
if you are a dual citizen of one of those countries travelling to the US from OUTSIDE those countries then the order does not apply to you
The only dual nationals who might have extra checks are those coming from one of the 7 countries themselves – for example a UK-Libya dual national coming from Libya to the US.
The US has reaffirmed its strong commitment to the expeditious processing of all travellers from the United Kingdom.
Since issuing this advice we have received further confirmation from the US government that British passport holders (regardless of country of birth or whether they hold another passport/nationality) are not affected by the executive order.