The team was contacted before the public announcement of the Queen Mother's death at the end of last month and met with other authorities running the proceedings – including the Metropolitan Police, Westminster council and the Royal Household – the morning after the announcement.
The firm oversaw the erection of 65 media stands in London and Windsor, which gave photographers opportunities to capture the procession on film. It also put up 30 toilets.
A source close to the EC Harris team, which worked for the Department for Culture, Media and Sport, said the operation had been a taxing one. He said: "The logistics of the whole operation were huge. They had to make alterations right up to the last minute to the plans. The feedback from all parties involved has been tremendous."
The funeral was attended by 2300 guests. More than a million people also lined the 23-mile route of the Queen Mother's last journey from London to Windsor, with many throwing flowers at the hearse as it passed.