The volunteers – each playing the part of one of the 19,240 British soldiers who fell on the first day of the Battle of the Somme, exactly 100 years ago – appeared at train stations, shopping centres and other public places across the UK.
Members of the public were given cards by the volunteers, which showed details of the soldiers they were representing, and the hashtag #wearehere, but no information as to who was behind the stunt.
The emotive event created huge buzz on social media, and Twitter and Instagram posts were collected on the website becausewearehere.co.uk. During the day it did not provide any clue as to the organisation of the performance, but has since been updated with further details.
During the day, PRWeek contacted a number of the organisations believed to be involved – all either claimed to have little information themselves, or said they would not reveal more information until an announcement was made that evening.
Arts PR specialist Bolton & Quinn – whose co-founder was named one of the 1,000 most influential Londoners last year – was providing support to the event, but declined to give further details when contacted on Friday itself, or over the weekend.
From 7am in the morning the volunteers – none of whom were trained actors but included a range of professions – spent 12 hours travelling around and between various locations, interacting with the public and singing.
The performance was then revealed to have been a piece led by 2004 Turner Prize winner Jeremy Deller.
Deller worked with National Theatre director Rufus Norris to create what was one of several "extraordinary arts experiences" overseen by WWI commemoration organisation 14-18 Now, which has lottery and Arts Council funding and Department for Culture, Media & Sport (DCMS) backing.
"The volunteers worked for weeks under the strictest secrecy to ensure the performance was delivered in a powerful and unexpected way. This is the first time the three national theatres have worked together on a joint project, and the first time so many theatres have worked together on a UK-wide participation project," according to the 14-18 Now website.
The project took a year to plan and was "one of the largest arts participation projects ever staged in the UK", it says.
Alongside the National Theatres of England, Scotland and Wales, a variety of charities, arts organisations and theatres helped co-ordinate Friday's performance, as did the BBC and Network Rail.
The events were covered across national media, with some papers publishing information about the men who died.
The DCMS said that in addition to supporting #wearehere, the department itself had managed comms around commemorative events in France, Manchester and London.
Central to this was a film tribute featuring Somme descendants ranging in age from five to 87, reading from the poem For The Fallen by Laurence Binyon. The department's comms team managed to arrange for this to be broadcast for free in Piccadilly Circus, the All England Lawn Tennis Club in Wimbledon, train stations and airports and other locations, ahead of the national two-minute silence on Friday morning.
It said there were an estimated one billion impressions on digital media of its hashtag #Somme100 through the day.