An appropriate governmental website tells me that to apply for an NI number*, I must go to my nearest Job Centre or Social Security office and apply in person; when the office is unable to locate an existing NI number for me, I will be scheduled for an interview.
I diligently look up and map the route to my nearest Job Centre. I walk there. It's 3:45 and the office is closed. The posted open hours are from 9 am - 5 pm, which I am clearly there between. A sign in the window lists numbers to call, depending on needs. I walk home and call the relevant number. It rings and rings and rings. No answer.
* National Insurance number. Just like a SSN or a SIN.