This article was written three months ago and just published in crowd magazine but is an interesting and still relevant read nonetheless. It provides a useful answer to the question What is Crowd Management? A question that we will all need to answer for our events in the months to come.
https://www.thecrowdmagazine.co.uk/crowd-safety/what-is-crowd-management/
Both you and I Mark have experienced large scale people movement and this will provide us with invaluable insight for safe social distancing crowd management, however this manifests itself.