I found this it turns out the opening of the Embassy is scheduled for the 16th January, don't know about staffing,but if it is opening on Tuesday on the 16th then safe too say some staff would be there onsite maybe,
here is the link
www.dailymail.co.uk/news/article-5175103/Inside-new-750m-Embassy-London.html
there are no travel advisories that I can see but it is a new building requiring at least 800 staff, would they be all their day one. I am not sure just speculating.
travel.state.gov/content/travel/en/traveladvisories/traveladvisories.html
do we need a spiderweb built for Saud, Roths and Soros separately,
Then see where they overlap?