Sergeant Saltwell shared a picture of the card on Twitter as he revealed every officer in Westminster received the heartfelt thank you note from a citizen known only as Hasnain.
The card said: “Dear officers,
“Thank you for keeping us safe!
“We appreciate it all.”
Sergeant Saltwell said a member of the public handed the police officers at Westminster thank yous London Terror Attack: Latest Pictures Thu, March 23, 2017
4 dead and 40 injured in Westminster terror attack
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Conservative MP Tobias Ellwood (centre) helps emergency services attend to a police officer outside the Palace of Westminster, London
Sgt Saltwell posted a picture of the note with the caption: “I’m currently on the policing operation in @MPSWestminster. A member of the public has just given each of us one of these. #WeStandTogether.”
Emergency services responding to the tragedy have received huge praise.
The thank you note photo which was given the police officer was posted to Twitter
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How the London terror attack happened
Thank you for keeping us safe!
Commons Speaker John Bercow also commented: “[Pc Palmer] was killed defending us, defending Parliament and defending parliamentary democracy.”
Mrs May continued: "The police heroically did their job.
"We will remember the exceptional bravery of our police, security and emergency services who once again ran towards the danger even as they encouraged others to move the other way.
"On behalf of the whole country I want to pay tribute to them for the work they have been doing to reassure the public, treat the injured and bring security back to the streets of our capital city.”
London terror attack victims Thu, March 23, 2017
ISIS claims responsibility for London attack that killed at least three victims
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Emergency services rushed the scenes in central London after the attacker, later identified as Khalid Masood, drove his car through pedestrians on Westminster Bridge before forcing his way into the grounds of Houses of Parliament.
Police shot Masood who died at the scene.
Tributes to heroic doctors, nurses and police have also been shared across social media.
Emergency services responding to the scene at Westminster How the front pages of newspapers are reporting the London terror attack Thu, March 23, 2017
Media across Europe, to the USA, the Middle East have paid tribute to the victims
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Soph Findlay on Twitter wrote: “So much respect for the doctors and paramedics who ran into danger to help. Real heroes #Westminster #Parliament #PrayForLondon”.
Parveen Agnihotri added: “Kudos to the doctors and nurses who ran to #Westminster bridge to save lives of those injured. Our emergency services especially the police did us proud.”
A candlelit vigil was held in Trafalgar Square with thousands of people turning up to pay their respects to the victims on Thursday night.