I interviewed for a B1/B2 US visa back in June, and was issued a 221(g) form in seconds. Judging from the experiences of hundreds of others in the same situation, I will have to wait for them to screen for security concerns (i.e. administrative processing) before I can get the visa. On average, the wait is about one month, but it can often stretch months longer, and I cannot do anything to expedite the process before 180 days of waiting. Meanwhile, my visa status on https://ceac.state.gov/CEACStatTracker/Status.aspx looks like this:
Around the same time, I applied for an High Potential Individual (HPI) visa from the UK, because I did not anticipate the delay for the US visa. This visa gives me the right to work, and some UK employers I interviewed with indicated they would hire me if I could start within a month.
I submitted the HPI application form, paid for the visa, but postponed the UK visa interview several times due to the delay with my US visa application. I know several cases where people stuck in admin processing "borrowed" their passports from the US embassy, and successfully applied for other visas in the meantime. But I'm concerned that UK consular officials might be able to see the current status of my US visa application through special info-sharing schemes, and mistakenly conclude that I hid the fact that I was "refused" a US visa. I am also concerned that even if I withdraw my US visa application, the status might stay stuck in the "refused" state. Please kindly advise if that is true.
Other potentially relevant info: I hold a valid US visa and a Canadian visa.
Update: I included a cover letter among my attached materials, and I was approved by the UK Home Office in 3 days without expedited processing.