Number of spectators calculated by Professor Keith Still and his team
Crowd science experts from Manchester Metropolitan calculated around 400,000 well-wishers lined the streets of Windsor for the royal wedding.
The team estimate that at its peak between 390,000 and 423,000 spectators turned out to catch a glimpse of Prince Harry and Meghan Markle after the pair tied the knot on Saturday at St George’s Chapel at Windsor Castle.
The lecturer-and-student team at Manchester Metropolitan University, led by Keith Still, Professor of Crowd Science, studied photographs and news feed footage of the assembled masses while the newlywed Duke and Duchess of Sussex enjoyed an open top carriage ride following their marriage ceremony.
In order calculate the number of spectators their analysis takes into account a range of factors such as the capacity of open spaces along the parade route.
Such an approach was previously employed by the team to calculate the attendance at President Donald Trump's inauguration ceremony in January 2017 and size of the crowd at the hometown victory parade for the Phildelphia Eagles in February this year following the club's historic win of the Super Bowl, the end-of-season championship game in American football.
Prof Still said: “We estimated the crowd size at 390,000 to 423,000 and therefore more than two times the number of people that attended Trump's inauguration.
“Trump’s inauguration crowd occupied around 61,000 square metres of space (standing/seated) and the royal wedding spectators filled around 100,000 square metres (packed standing).”
Prof Still added: “We use images and ground projection, typically using Google Earth Pro and our own 3D software, to assess density from 3D projections that reconstruct the angles and lines of view.
“It is part of a technique called crowd modelling in which we also consider routes, areas, movement over time and the people and profile of the crowd.
“The University teaches these processes, and our MSc Crowd Safety and Risk Analysis team has evaluated crowd sizes for the last two years.
“We are often asked by officials around the world to evaluate the actual numbers against the political numbers, which can often be exaggerated.”
The royal wedding was one of the first times the police could put into practice the knowledge, understanding and skills taught in a new Event Module training course for senior police officers for which Professor Still produced material on crowd management.
He routinely uses computer modelling to help organisers and law enforcement agencies prepare for the presence and movement of throngs of people and to keep them safe.
Prof Still said: "Over the last 20 years, we have been teaching the principles and applications of crowd science around the world.
"This covers the topics of crowd safety and risk analysis for places of public assembly.
"Following discussions with the College of Policing, we wrote a short course that aligns with our MSc programme in Crowd Safety and Risk Analysis as part of the CPD (continuous personal development) programme for Public Events Commanders (PEC) course.
"The progression from the PEC’s course, through an APEL course (online or face to face) then to the MSc programme at Manchester Metropolitan is a pathway designed for the College of Policing.
"We are now working with other international police forces on a similar CPD programme."
Besides crowd modelling, the course covers risk analysis; the role of partner agencies; and includes contributions from subject matter experts such as events promoters, the UK Football Policing Unit and the Sports Grounds Safety Authority.
While the course had been designed and created by the College of Policing for forces in England and Wales, it is delivered at regional training centres licensed by the College.
The course is a mandatory requirement for all Gold, Silver and Bronze commanders, and tactical advisers, as part of their registration with the College for national operational accreditation. Those undertaking the course only complete it after passing a final assessment on the content.
Prof Still is a leading expert in the field of crowd science and risk assessment and his insight has been in high demand recently: estimating historical crowd sizes of previous US presidential inaugurations for the New York Times, from Lincoln to Obama.
In December, he provided analysis for the Washington Post on the safest number of people that New York’s Times Square could hold for New Year’s Eve celebrations.