text: **4.**An official of a foreign Government, required to travel to the United Kingdom to undertake 
  essential border security duties, or a contractor directly supporting these essential border security 
  duties where— 
  
  (a) they are in possession of a written notice signed by a senior member of their foreign 
  Government confirming that they are required to undertake essential border security 
  duties in the United Kingdom within the period during which they would, but for this 
  paragraph, have had to self-isolate in accordance with regulation 9 and that that work 
  cannot be undertaken whilst the person is complying with regulation 9; or 
  
  (b) their deployment is pursuant to a standing bilateral or multilateral agreement with Her 
  Majesty’s Government on the operation of the Border controls within the United 
  Kingdom. 