US Correspondent Emma Murphy reports on the country preparing to remember a day that changed history
Most people who are old enough remember exactly where they were or what they were doing the moment they learned of the terrorist attacks on September 11, 2001.It is hard to believe 20 years has passed since one of America's darkest days in history.
On Saturday, events are taking place across the US and around the world to remember those who lost their lives- a total of 2,977 people, including 67 Britons.
There will be an official service of remembrance at Ground Zero, the site of the Twin Towers, attended by the US President Joe Biden and First Lady Jill Biden as well as many families of those who were lost that day.
Six moments of silence will mark the times when each of the World Trade Center towers was struck, when each fell, and the time corresponding to the attack at the Pentagon, and the crash of the US Flight 93 in Pennsylvania. Ceremonies will also take place at the Pentagon and in Pennsylvania where flight 93 came down after passengers on the plane fought back against the terrorists. It will take three hours to read the names of the dead.
On the eve of 9/11 President Biden released a video to mourn the ongoing losses. “Children have grown up without parents, and parents have suffered without children,” Mr Biden, a childhood friend of the father of a September 11 victim, Davis Grier Sezna Jr. But the president also spotlighted what he called the “central lesson” of 9/11, “that at our most vulnerable, unity is our greatest strength.”
The September 11 UK Families Support Group is holding a 20th anniversary Special Service of Remembrance for bereaved families who lost loved ones in the attacks.
The private gathering will take place at the September 11 Memorial Garden in Grosvenor Square, London.
After sunset LED candles will be lit in memory of those who died, which will be open to the public.
At the Guard Change at Windsor Castle, members of the military played the US national anthem as they were watched by delegates from the American embassy.
Ahead of the commemorations, the Queen sent a message to Mr Biden, saying her thoughts are with all the victims, survivors, first responders and their families.
“As we mark the 20th anniversary of the terrible attacks on September 11 2001, my thoughts and prayers — and those of my family and the entire nation — remain with the victims, survivors and families affected, as well as the first responders and rescue workers called to duty," the Queen said in her message to the US president.
“My visit to the site of the World Trade Centre in 2010 is held fast in my memory.
"It reminds me that as we honour those from many nations, faiths and backgrounds who lost their lives, we also pay tribute to the resilience and determination of the communities who joined together to rebuild.”
A separate event at the Olympic Park in east London on Saturday will have a televised address from Prime Minister Boris Johnson in which he will say recent events in Afghanistan "will only strengthen our determination to remember those who were taken from us".
In the pre-filmed video, Mr Johnson will say: “Twenty years ago, September 11, 2001 became, in President Roosevelt’s words after Pearl Harbour, a ‘date which will live in infamy.'
“On a crystal clear morning, terrorists attacked the United States with the simple goal of killing or maiming as many human beings as possible, and by inflicting such bloodshed in the world’s greatest democracy, they tried to destroy the faith of free peoples everywhere in the open societies which terrorists despise and which we cherish.
“And it is precisely because of the openness and tolerance of the United States that people of almost every nationality and religion were among the 2,977 murdered on that day, including 67 Britons, each of them a symbol of the eternal friendship between the United Kingdom and the United States.
“But while the terrorists imposed their burden of grief and suffering, and while the threat persists today, we can now say with the perspective of 20 years that they failed to shake our belief in freedom and democracy; they failed to drive our nations apart, or cause us to abandon our values, or to live in permanent fear.
“The fact that we are coming together today – in sorrow but also in faith and resolve – demonstrates the failure of terrorism and the strength of the bonds between us.
“Recent events in Afghanistan only strengthen our determination to remember those who were taken from us, cherish the survivors and those who still grieve and hold fast to our belief in liberty and democracy, which will always prevail over every foe.”
Labour Party leader Keir Starmer said the anniversary was "to show support to our American friends."
He will say: "20 years ago today the world was in shock as we witnessed an unprecedented and despicable act of violence on US soil.
“9/11 saw the deadliest terrorist attack in history with almost 3,000 people tragically murdered including 67 people from the UK."
“Today we remember and honour them. We show support to our American friends as they mark this difficult time in their history.
“And we remember those in all corners of the world who have lost their lives to terror. They will always be in our hearts and our memories.
“The consequences of the 9/11 attacks are still being felt to this day.
“The tragedy is still so raw.
“But as we mark this anniversary I’m convinced our resolve has never been stronger.
“We will continue to fight terror and violence ...by promoting our values of justice and peace.”