A year to the day after the Westminster attack, memorials have taken place to remember the victims and survivors of the four terrorist attacks across London in 2017.
Fourteen people were killed and more than 100 others injured in attacks in Westminster, London Bridge and Borough Market, outside Finsbury Park mosque and at Parsons Green tube station.
Theresa May laid a wreath of flowers on Parliament Square, with a handwritten note which read: "In memory of those who were lost, and in defiance of those who would seek to silence democracy".
In the chambers of the House of Commons, MPs from all parties observed a minute's silence "in respectful memory" of those who died.
Marking the memory of those who passed away, Culture Secretary Matt Hancock thanked "the emergency services who keep us safe…and put others' safety ahead of their own".
He went on, "We remember those who have lost their lives defending democracy. They will not be forgotten."
Speaking at City Hall, London Mayor Sadiq Khan said: "Londoners will never forget the horrific terror attacks on our city in 2017. We will never forget the bravery of our emergency services and first responders who ran towards danger while urging the rest of us to run to safety.
He went on, "And we will never forget the courage of PC Keith Palmer, who paid the ultimate sacrifice whilst protecting Parliament."
Five people were killed and more than 50 injured when Kent-born Khalid Masood drove a car into pedestrians on the south side of Westminster Bridge, before fatally stabbing PC Palmer in New Palace Yard.
MP and trained medic Tobias Ellwood treated the police officer at the scene, but his life couldn't be saved.
The four people killed on the bridge were American tourist Kurt Cochran, Romanian tourist Andreea Cristea, 31, and Britons Aysha Frade, 44, and 75-year-old Leslie Rhodes.
Masood, 52, was shot dead by armed police at the scene.
One year on, fellow officer PC Shaun Cartwright, who was arriving at work to take over guard from PC Palmer, has paid tribute to his friend.
Describing the moment he was told of the attack, PC Cartwright told Sky News: "I didn't know who it was. I asked a few people, but I don't know if they didn't want to tell me or they didn't know. Finally someone told me, it's your friend Keith.
"I knew by then that he'd gone. I lost a really good friend. Considering the jobs that we'd done before on the Territorial Support Group (TSG) – drugs raids and rapid entries – you can almost imagine it happening there but not at the Houses of Parliament.
"Wherever he was he enjoyed work. He always came in with a smile on his face and just wanted to get on and do his best. I'd have liked to have my friend beside me rather than attending his funeral. It's not the way it should be. He was proud to be a policeman."
A service of commemoration also took place in Westminster Hall, attended by attended by politicians, senior police officers and people involved in the incident.
Led by the Reverend Jonathan Osborne, the senior chaplain to the Metropolitan Police Service, a blessing was also given by the Archbishop of Canterbury, Justin Welby.
Archbishop Welby told the gathering: "A year ago, darkness struck across Westminster Bridge and in this palace. It spread across the bridge like a snake, driving to left and right, killing and harming."
Reverend Rose Hudson-Wilkin, the Speaker's chaplain, told the service: "A year ago today on this estate and on Westminster Bridge we were visited by what I regard as evil."
Rev Hudson-Wilkin praised PC Palmer, saying he "ran towards the danger in order that we might be safe".
One year on, I will be remembering those affected by the Westminster attack. The professionalism of the emergency services and the bravery of PC Keith Palmer on that day will never be forgotten and my thoughts continue to be with the victims and their families #LondonUnited
— Amber Rudd MP (@AmberRuddHR) March 22, 2018
Ahead of the service, the Home Secretary Amber Rudd tweeted: "One year on, I will be remembering those affected by the Westminster attack. The professionalism of the emergency services and the bravery of PC Keith Palmer on that day will never be forgotten and my thoughts continue to be with the victims and their families #LondonUnited".
More from Finsbury Park attack
Later, #LondonUnited will be projected onto the four locations where the attacks took place.
A digital book of condolence will be open to the public until 19 June, when it will become part of a 3D installation in City Hall.