It's one of the biggest gatherings of world leaders in one location in living memory, prompting a massive security operation throughout London and the UK.

London police chiefs and medics are bracing themselves for a security nightmare at the Queen's funeral on Monday as they balance the need to protect the world's top leaders and dignitaries with the public's desire to mourn their much-loved monarch.

Some have compared the event in scale to the London Olympics, but in truth the state funeral – the first in Britain since Winston Churchill died in 1965 – is likely to dwarf the 2012 sporting extravaganza.

Codenamed "Operation London Bridge," arrangements for Britain's longest-serving monarch have been carefully pored over for years by the many agencies involved, with the Queen herself signing off on every detail before her death.

READ MORE: The order of service for the Queen's funeral

The city has already seen unprecedented crowds viewing the official lying-in-state, which will run until 6.30 am (3:30 PM AEST) on Monday, just hours before the funeral procession to Westminster Abbey commences.

The sheer numbers caused queueing to be temporally paused on Friday.

In an interview with Sky News earlier this week, London Mayor Sadiq Khan said of the scale: "If you think about the London marathon, the carnival, previous royal weddings, the Olympics – it's all that in one."

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The three police forces which operate in the British capital – the Metropolitan Police, the City of London Police and British Transport Police – initiated their well-rehearsed plans across London as soon as the death of Elizabeth II was announced on September 8.

The funeral will be the "largest single policing event" that London's Metropolitan Police force has undertaken, its Deputy Assistant Commissioner Stuart Cundy told reporters Friday.

"As a single event, this is larger than the 2012 Olympics. It is larger than the Platinum Jubilee weekend. And the range of officers, police staff, and all those supporting the operation is truly immense," he said.

It is also set to "be the largest global protection operation the Met Police has ever undertaken" as "hundreds of world leaders and VIPs" descend upon London, he said.

READ MORE: World leaders head to London for Queen Elizabeth II's funeral

When asked specifically how high-profile guests would be transported to London's Westminster Abbey for the funeral service, Cundy declined to give specific details, saying it would not be conducive to a "safe and secure event and policing operation."

Meanwhile the mammoth logistical operation has involved myriad other aspects, such as medics, toilets, street cleaning and road closures.

The size of the crowds turning out to pay their last respects is "impossible" to predict, according to Andy Byford, commissioner for Transport for London (TfL).

Byford described the funeral as "the biggest event" the transport network has ever faced in an interview with Britain's PA Media news agency.

Comparing it to the Olympics, he said: "This is more challenging. It's over a long period and although there are estimates, it is impossible to say with certainty how many people will turn up to the various elements, so we've assumed the highest possible number and we're aligning our service to match that."

Invitations have been sent to world leaders, politicians, public figures and European royals, as well as more than 500 international dignitaries. The security considerations are mind-boggling.

The British government is taking the lead on logistics but has refused to comment on specific "operational security arrangements."

US President Joe Biden was among the first to confirm his attendance at the event, which will be attended by up to 2,000 people. Japanese Emperor Naruhito and Empress Masako will also travel to London, as will many other royals and global leaders.

Hundreds of police officers from other forces are supporting the Met, yet the attendance of so many VIPs will pile on the pressure.

"Everything will have been negotiated," said Morgan, explaining that some concessions will have been made.

There simply aren't enough police and protection officers to give an escorted convoy to everybody who would normally get it on a standalone visit. Therefore people are being put together on a logistical basis," Morgan said continued.

Simon Morgan is a former royalty protection officer who was responsible for overseeing senior royals including the Queen and new King between 2007 and 2013.

"It will be seamless," Morgan, who now runs private security firm Trojan Consultancy, told CNN.

"The policing plan and security behind it is a two-fold operation: security and public safety are both intrinsic."

Morgan said the events surrounding the state funeral have been in the pipeline for decades.

"London Bridge came to fruition in the 60s. It's been subject to review at least three times a year.

"Elements are discussed and indeed some elements have been already used in isolation," he said, citing the Queen Mother's funeral in 2002, royal weddings and the Platinum Jubilee as examples.

Regular reviews were vital in combating the changing nature of security threats – from Irish nationalism in the 1970s and 80s, to Islamic extremism more recently.

White House aides have declined to provide specific security details for President Biden's visit, but say they are working with their British counterparts to ensure the demands of presidential security are met. The FBI will monitor potential threat streams and share any information with UK security service MI5.

When reports emerged last week that world leaders would be required to ride on a bus to the funeral, US officials were skeptical and shot down the suggestion Biden would travel to Westminster Abbey in a coach.

In 2018, when other world leaders traveled together in a bus to a World War I memorial in Paris, then-US President Donald Trump traveled separately in his own vehicle.

The White House explained at the time the separate trip was "due to security protocols."

"Everything will have been negotiated," said Morgan, explaining that some concessions will have been made. There simply aren't enough police and protection officers to give an escorted convoy to everybody who would normally get it on a standalone visit. Therefore people are being put together on a logistical basis," Morgan said.

"There's no compromise in relation to security and a lot of visiting dignitaries will be very aware of the optics of demanding their own protection teams."

Police must also consider the "fixated threat," he said.

"That's someone who is fixated on a member of the royal family. A lot of those people are subject to mental health orders and subsequently came to the attention of medical professionals and sometimes law enforcement."

"Single cause" activists also pose a risk, Morgan said.

The force has already come in for harsh criticism over its treatment of republican protesters.

"Every single one of these causes wants to use global media attention to highlight what's important to them," he added.

Symon Hill, from Oxford, told CNN how he was aggressively arrested after calling out "not my King" at a ceremony which proclaimed Charles III's accession.

He said he had been left "gobsmacked" after "police intervened, grabbed hold of me, handcuffed me, and put me in the back of a police van."

He added: "Surely arbitrary arrest is not something we should have in a democratic society."

According to Morgan, police aim not to ban peaceful protests but ensure public order, as demonstrations can sometimes provoke confrontation when emotions are running high.

"The police are very much in a 'damned if you do, damned if you don't' situation," he said.

While police are spearheading the operation, many others are closely involved – among them military, transport and utility bosses.

Concerns over health are paramount.

As well as the official emergency services, around 2,000 volunteers and employees from St. John Ambulance have provided 24-hour support in London and Windsor for the lying-in-state, as well as her funeral.

"In our planning for this sad occasion, we estimated we'd need around 1,000 volunteers, but more than double that have said they can make themselves available," St. John Commissioner of Operations Mike Gibbons said in a statement.

Patrick Goulbourne, assistant commissioner, operational resilience and control, at London Fire Brigade, told CNN his team worked "over many years with partners."

They have carried out fire safety inspections on over 40 key central transport hubs and have also been carrying out around 160 fire safety inspections a day at hotels, restaurants, shops and more. In addition, there have been 10 fire engines and around 50 firefighters assisting people in line to see the Queen's coffin around the clock.

King Charles III has issued a public statement of thanks after 10 days of public mourning for his mother, Queen Elizabeth II.

The late monarch's lying in state at Westminster is set to come to a close in the coming hours, with thousands of people having passed through to pay their respects.

The official funeral service is set to begin tomorrow (tonight AEST).

LIVE UPDATES: Entire country falls silent to honour Queen on eve of funeral

"Over the last ten days, my wife and I have been so deeply touched by the many messages of condolence and support we have received from this country and across the world," Charles said in a statement.

"In London, Edinburgh, Hillsborough and Cardiff we were moved beyond measure by everyone who took the trouble to come and pay their respects to the lifelong service of my dear mother, the late Queen.

"As we all prepare to say our last farewell, I wanted simply to take this opportunity to say thank you to all those countless people who have been such a support and comfort to my Family and myself in this time of grief."

READ MORE: World leaders head to London for Queen Elizabeth II's funeral

READ MORE: Man charged after allegedly rushing at Queen's coffin

Up to 10,000 police have descended on London ahead of the funeral, along with world leaders and dignitaries from across the globe.

The queue to view the Queen's coffin has stretched to 24 hours, with people being asked to stop joining it or risk not making it into Westminster.

The Queen’s eight grandchildren, led by heir to the throne Prince William, circled the coffin and stood with heads bowed during a silent vigil on Saturday evening. 

Crowds also gathered Sunday near Windsor Castle, where the Queen will be laid to rest at a private family ceremony on Monday evening.

A strong earthquake shook Taiwan on Sunday as a series aftershocks hit the self-governing island off China's east coast.

The 6.8 quake struck at a relatively shallow depth of seven kilometres near the city of Taitung on the southeastern coast, Taiwanese authorities reported.

A two-story residential building collapsed near the epicentre, according to a Taiwanese media report. The shaking was felt at the north end of the island in the capital, Taipei.

https://twitter.com/willripleyCNN/status/1571392400890953728

Following the quake in Taiwan, Japan Meteorological Agency issued an advisory for a tsunami as high as one metre reaching several southern Japanese islands. Weather officials urged residents in those areas to stay away from the coastline.

The agency said the earliest waves could reach the Yonaguni island, Japan's westernmost island about 250 kilometres northeast of Taitung, at 4.10 pm local time (5.40pm Australian time) and subsequently three nearby islands.

A 6.4 earthquake hit Taiwan on Saturday night in an area north of Taitung County that has been rattled by numerous aftershocks since then.

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A bus overturned on an expressway in southwestern China on Sunday, leaving 27 people dead and injuring 20 others, police said.

The early morning accident was in Sandu county, which is southeast of the city of Guiyang, the capital of Guizhou province, a brief police statement said.

The bus had 47 people on board and the injured were being treated. No other information was immediately released.

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If you love space and exploring the cosmos, there is no shortage of wonder right now.

Scientists identified mysterious diamonds that likely originated from a dwarf planet that once existed in our solar system – until it collided with a large asteroid 4.5 billion years ago.

The rare space diamonds aren't the only find mesmerizing researchers.

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A "breathtaking" image captured by the James Webb Space Telescope is revealing the secrets of star birth in the Orion Nebula.

Expect to see more unprecedented Webb images in the coming weeks.

Meanwhile, the Artemis I mission has a new launch date scheduled for September 27, with a 70-minute window that opens at 1.30am.

And on Mars, inspiring discoveries are afoot as the Perseverance rover investigates an intriguing site.

Other worlds

The Perseverance rover has made its most exciting find on the red planet to date.

Perseverance has finally collected samples from the site of an ancient river delta, which is full of rock layers that serve as a geological record of the Martian past.

Some of the rocks include the highest concentration of organic matter found by the rover to date, according to NASA scientists.

Among the organic matter are minerals that correlate with sulfates, which could preserve evidence of once potentially habitable sites on Mars and the microbial life that may have existed there.

New photos show the promising rocks amid the delta's alien landscape.

These important samples could answer the ultimate cosmic question: Are we alone in the universe?

We are family

Modern humans and Neanderthals lived in tandem until our ancient relatives went extinct about 40,000 years ago.

Now, researchers think they may have pinpointed something that gave Homo sapiens a cognitive edge over the Stone Age hominins.

Scientists discovered a genetic mutation that may have allowed neurons to form faster in the modern human brain.

"We've identified a gene that contributes to making us human," said study author Wieland Huttner, professor and director emeritus at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany.

But some experts think more research is needed to ascertain the gene's true impact.

Trailblazers

What's good for the goose is good for the gander and these golden geese have provided some pretty significant benefits.

Three teams of scientists won the 2022 Golden Goose Awards, prizes organised by the American Association for the Advancement of Science, for pioneering breakthroughs.

One of those includes the Foldscope, a microscope made from paper that costs $1.75 to make.

Stanford University bioengineer Manu Prakash came up with the idea on a research trip in the Thai jungle more than a decade ago.

The scientific instrument has traveled around the world, and researchers have even used it to identify a new type of cyanobacteria.

Defying gravity

Mark your calendars: A NASA spacecraft will intentionally crash into a tiny asteroid on September 26.

The Double Asteroid Redirection Test spacecraft, or DART, launched in November and is on its way to a rendezvous with Dimorphos, a small moon orbiting an asteroid called Didymos.

The mission will nudge the asteroid, which poses no threat to Earth, to change its speed and path in a first-of-its-kind test of kinetic impact.

If DART is successful, the mission could demonstrate future ways to protect Earth from space debris.

The spacecraft recently got its first glimpse of Didymos from about 32.2 million kilometres away.

On the day of the encounter, we'll see Dimorphos for the first time before DART collides with the space rock.

Consequences

The Xerces blue butterfly, Floreana giant tortoise and Tasmanian tiger are just some of the species that the world has lost due to human-driven threats.

Environmental and travel photographer Marc Schlossman has spent 15 years documenting extinct and endangered animal specimens in Chicago's Field Museum collection for his new book, "Extinction: Our Fragile Relationship With Life on Earth."

Schlossman provides a glimmer of hope at a time when biodiversity loss is accelerating. Of the 82 species photographed for the book, 23 are extinct, he said.

Thanks to conservation efforts, the rest have been brought back from the brink of disappearing or, as in the case of the New Zealand kākāpo, can recover with "robust" conservation work.