Image source, Getty Images

The horrors of 9/11 will never leave me, writes Director General of MI5 Sir Ken McCallum in the Independent this morning., external

The head of the UK's domestic intelligence and security agency says it was apparent after the attacks that "al-Qaeda had to be not just taken on, but taken down".

The Islamist extremist network, while still a threat, now has capabilities that are "a fraction of 2001's" thanks to a "gargantuan multinational effort, powerfully spearheaded by the US", McCallum says writes.

He also notes that the MI5 in 2026 contends with "a threat landscape markedly different" than 25 years ago - but adds that the agency "seeks to bring the same unflinching resolve and willingness to adapt that carried us through the traumas of the 9/11 era".

He concludes: "We owe the victims of 9/11 - and those who will otherwise become the victims of tomorrow’s attack - something more than remembrance. We owe them preparation, resilience and the courage to adapt before the next shock arrives."

Brendon Williams
BBC News

Image source, Charles Wolf

Charles Wolf knew immediately that something was wrong when a plane flew low over his New York City apartment on a sunny morning 25 years ago.

Seconds later, the plane slammed into the North Tower of the World Trade Center - where his wife Katherine, from Swansea, was working.

Katherine died instantly, becoming one of 2,977 people killed in the al-Qaeda terrorist attacks on the USA on 11 September 2001.

"I knew instantly when it flew over my building - our apartment building - that it was a twin engine jet at full throttle," said Charles, a trained pilot. "I knew it so well that I called the FBI and told them... 'That was no accident, that was deliberate'."

A year later, when Charles met the FBI agent who took that call, he said the agent told him: "You were the first person to get us on to the fact that that was not an accident."

Charles subsequently led a campaign to ensure the victims' families and dependants were fairly compensated, and said his "wonderful" wife would be proud of what he fought for.

Unhappy with the US-government run September 11th Victim Compensation Fund, he successfully pressured the authorities into allocating funds more fairly and to more people.

His fight later became the subject of a Netflix movie called Worth, in which he was portrayed by the actor Stanley Tucci.

Warning: This post contains details that some may find distressing

Janice Brooks had only moved to New York a couple of weeks before 9/11 to begin what she calls "the biggest adventure of [her] life" - working for a company called Euro Brokers on the 84th floor of the South Tower.

On the morning of the attacks, she was in the office when she heard a bang and saw "paper and dust swirling" as the first plane hit the North Tower, she tells BBC Breakfast.

While she was evacuating, the second plane hit with an "almighty thud". Brooks heard "one of those horror film screams" as a woman was hit by debris, her eyes covered in blood.

She says the scream "lives in my head".

When she finally reached the ground floor and looked up at the building, there was a "big gaping hole" where her floor should have been.

Sixty-one people died in her office. "I only went to 23 funerals," Brooks says. "I should have tried harder, I’ll take it to my grave that I let them down."

She says she's given herself "one job" since that day: "To have a good life".

A day that "changed the landscape of the country" and "something that we all should remember".

Those are some of the words Americans have chosen to describe the 9/11 terror attacks 25 years on.

One man recalls waking up that day, "getting a phone call, turning on the TV and just crying".

Another woman describes the "heartbreaking" moment she saw footage of the towers falling.

Across America, people have already been paying tribute to the victims of 9/11.

It's been 25 years since the attacks and commemorative events and displays have lit up the sky above New York and nearly 3,000 US flags have been laid in the shape of the Twin Towers in North Carolina.

Here are some of the pictures we've seen so far:

Image source, Getty Images

Image source, Getty Images

Image source, Reuters

How the lessons of 9/11 are still being learntpublished at 07:17 BST

07:17 BST

Frank Gardner
Security correspondent

Image source, Getty Images

The first duty of a government, countless leaders over the decades have said, is to safeguard its population. On 11 September 2001 the US manifestly failed to do that. The intelligence was there, yet tragically, nobody joined up the dots in time.

9/11, as the attacks on the US became known, came to define – along with the response – a generation of foreign, security and intelligence policy for the first two decades of this century.

In the ensuing 25 years there have been numerous intelligence successes as well as failures on both sides of the Atlantic. The successes include plots that have been foiled, suspects who have been arrested, brought to trial, convicted and jailed.

But what of the bigger picture? How has intelligence-gathering, counter-terrorism and strategic planning changed in the 25 years since the worst terrorist attack in US history?

• You can read my full analysis here

Image source, Reuters

In all, 2,977 people (not counting the 19 hijackers) lost their lives in the September 11 attacks, most of them in New York City:

• All 246 passengers and crew aboard the four planes were killed
• At the Twin Towers, 2,606 people died - at the time or later from injuries sustained during the attack
• At the Pentagon, 125 people were killed

The youngest victim was two-year-old Christine Lee Hanson and the oldest was 82-year-old Robert Norton, who were both passengers on planes.

Citizens of more than 90 different countries were among the casualties. New York City lost 441 first responders - the largest loss of emergency personnel in US history.

Thousands of people were injured, or later developed illnesses connected to the attacks, including firefighters who had worked in toxic debris.

Image source, Getty Images

United Flight 93 was the only plane that did not hit any targets during the attacks of 9/11.

The flight from Newark, New Jersey was headed west to San Francisco when four hijackers gained control of the aircraft and changed its flight path to travel south, heading towards the Washington DC area.

It is thought the hijackers had meant to attack Washington's Capitol Building - the attacks occurred days after US lawmakers resumed legislative activities after their traditional summer break.

The 40 passengers and crew onboard Flight 93 learned about the attacks in New York and at the Pentagon by communicating with friends and family on airfones.

They fought back against the hijackers who crashed the plane in an open field in Shanksville, Pennsylvania killing all on board and saving hundreds of lives.

A memorial, known as the Wall of Names, stands in the field where the plane crashed to honour the victims and the heroism they showed that day.

Image source, Getty Images

On Tuesday 11 September 2001, four planes flying over the eastern US were seized by small teams of hijackers from the Islamist extremist network al-Qaeda.

They were then used as giant, guided missiles to crash into landmark buildings in New York and Virginia. Two planes hit the Twin Towers of the World Trade Center in New York, with the second strike occurring 17 minutes after the first.

The buildings caught fire, trapping people on the upper floors, and enveloping the city in smoke. In less than two hours, both 110-storey towers collapsed in massive clouds of dust.

A third plane destroyed the western face of the Pentagon - the US military headquarters located just outside Washington DC.

The fourth plane crashed in a field in Pennsylvania after passengers fought back. It is thought the hijackers had meant to attack Washington's Capitol Building.

In all, 2,977 people (not counting the 19 hijackers) lost their lives, most of them in New York, including 441 first responders - the largest loss of emergency personnel in US history.

Image source, Spencer Platt/Getty Images

A series of memorials and vigils are being held across the US today, with the main events being held at the three sites where the attacks took place. Here's what to expect throughout the day:

In New York

• 08:30 US Eastern Daylight Time (12:30 GMT, 13:30 BST): A commemoration ceremony begins at the 9/11 Memorial plaza of the World Trade Center, during which the names of the victims will be read out from 08:46 EDT - the moment the first plane crashed into the North Tower
• The reading will be punctuated by seven moments of silence, six to mark the times the planes crashed and buildings fell, and the seventh to honour the first responders and survivors who have since died from 9/11-related illnesses

• 15:30 EDT: The New York Philharmonic Orchestra will perform a concert at the Perelman Performing Arts Center
• 17:00 EDT: A special memorial mass will be held at St Patrick’s Cathedral in Manhattan
• 19:00 EDT: The New York Yankees and the New York Mets will play a memorial game series to mark 25 years since the attacks
• TheTribute in Light will also be on display from dusk till dawn

In Pennsylvania

• 08:30 EDT: A ceremony will be held to honour the victims of Flight 93, which crashed in a field in Shanksville. The service will begin with a wreath laying ceremony, followed by a reading of the names of all 40 passengers and crew members who died

• 13:00 EDT: Speeches and musical performances will begin, before another wreath laying ceremony at the Wall of Names
• 19:30 EDT: 40 candle lanterns will be then be placed beside the wall in tribute to the victims

In Virginia

• 08:30 EDT: A community remembrance ceremony will be held in Manassas Park
• 09:00 EDT: President Donald Trump will attend a ceremony at The National 9/11 Pentagon Memorial, where he is expected to give an address

Image source, Getty Images

Today marks 25 years since the 9/11 attacks, as the world comes together to remember the 2,977 people who lost their lives.

On Tuesday 11 September 2001, suicide attackers hijacked four US passenger jets and crashed them into the Twin Towers of the World Trade Center in New York, which subsequently collapsed, and the Pentagon in Virginia.

The fourth plane crashed in a field outside Shanksville, Pennsylvania, after passengers fought back against the hijackers.

Twenty five years on from the attacks, which claimed the lives of people from more than 90 countries, their impact continues to be felt around the world.

A commemoration event is due to be held at 11:00 BST at the 9/11 memorial sculpture in London's Queen Elizabeth Olympic Park.

In the US, memorial events are being held throughout the day to honour those who lost their lives, including at the sites of the three attacks in New York City, at the Pentagon and in Pennsylvania.

The names of all 2,977 victims will be read out by relatives during a special ceremony at the World Trade Center at 08:30 EST (13:30 BST), which will be punctuated by seven moments of silence.

We'll bring you the latest updates throughout the day on how the anniversary is being marked in the US and around the world.