Inspector Rachael Robertson joined the complex security operation on the day the Queen’s coffin was flown down to London and the focus of the nation switched from Scotland to the capital.

Rachael and colleagues from Hertfordshire Police first met up with officers from all over the country at Hendon for operational briefings before getting to work the following morning.

She said: “We were there for eight days and performed various duties during that time. On the first day we were parading around Trafalgar Square and The Mall after the Queen’s coffin had spent the evening at Buckingham Palace ahead of the ceremonial procession to Westminster Hall.

“We then spent the next two or three days in and around Westminster, basically where the queues were, engaging with the people who had come to pay their respects.”

Rachael said the hundreds of thousands or people who queued for hours to see the Queen lying in state remained respectful and good-humoured throughout.

“The crowds were amazing,” she said. “I would describe it as the most positive engagement with the public I have experienced in the 21 years I have been a police officer.

“It was an absolute pleasure. Everyone wanted to be there for the same reason - to pay their respects - they were obviously very respectful of the Queen but also of the armed forces and the police.

“We didn’t encounter any negativity at all, it was all really positive and felt very collective. It was just a very positive experience.”

On the Saturday and Sunday before the funeral itself crowd numbers continued to swell but people remained good-natured as the mood grew more sombre and reflective.

“We always expected the weekend was going to be busier,” she said. “We were up and around Horse Guards and I have never seen London as busy.

“I spoke to a man who had lived in London for 30 years and he said he had never known it so busy. It was still very positive but you couldn’t move for the crowds.”

The day of the funeral saw Rachael and her colleagues move out of central London to patrol the route of the procession which took the coffin from Westminster Abbey to Windsor Castle.

She explained: “We were on the procession route by Cromwell Road and Earl’s Court in west London managing the crowds so we were lucky enough to have the cortege drive past us which was a very special experience.”

Reflecting on the part she played, Rachael - who capped off an extraordinary few days when she was presented with her long-service medal this week - said she doubted the experience would ever be matched.

“It was quite easily the best week I have had in my policing career and one I can’t see being emulated,” she said.

“It was a one-off thing and everyone there knew they were witnessing history. Obviously there will be kings and queens in the future but I think the impact the Queen had on people during her 70-year-reign was very special and I am proud to have been involved.”

Operation London Bridge was a huge policing and security operation which saw the biggest ever deployment of officers from across the UK, protecting crowds paying their respects as well as the hundreds of foreign dignitaries who attended the funeral.

More than 10,000 police officers were deployed on the day of the funeral itself as reinforcements from all over Britain worked alongside officers from the Met to ensure the ceremony and procession went without a hitch.

Hertfordshire Police sent around 100 officers to carry out patrols, security and other key police work in relation to the funeral and the period of mourning, during which hundreds of thousands of people from all over the world descended on London.

Matt Jukes, the head of UK counter-terrorism policing, said: “It is difficult to put into words the scale of the policing operation over the last 10 days, it has been nothing short of incredible.”