A National Police Memorial roll of honour in London lists all the officers who have been killed by criminal acts in the line of duty since 1680.
The roll records more than 1,600 officers who have died while performing vital tasks such as foiling terrorists, quelling rioters and marshalling protests.
Masood’s rampage – in which five people died – was ended when he was shot dead by a minister’s close protection officer. Pc Palmer was posthumously awarded the George Medal.
Also listed are the three unarmed Metropolitan Police officers murdered in Shepherd’s Bush by Harry Roberts in 1966.
Detective Sergeant Christopher Head, 30, Detective Constable David Wombwell, 25, and Pc Geoffrey Fox, 41, were shot without warning while questioning three suspects in a van.
In more recent times, Pc Gary Toms, 37, was critically injured confronting suspects in Leyton, east London, on April 11 2009.
He died six days later when his life support machine was switched off – 25 years to the day after Pc Yvonne Fletcher was shot dead outside the Libyan embassy in London while controlling a crowd of demonstrators.
Her killer has never been brought to justice and film director Michael Winner founded the Police Memorial Trust as a result of her murder.
Pc Fiona Bone, 32, and Pc Nicola Hughes, 23, were murdered by Dale Cregan in Greater Manchester in September 2012.
Pc Ricky Grey was shot in the head by a gunman who then turned the weapon on himself in Shrewsbury in 2007, and Pc Sharon Beshenivsky was shot dead when she and a colleague tried to stop armed robbers in Bradford in November 2005.
Another name on the roll is Pc Keith Blakelock, a 40-year-old father of three who was set on by a mob and hacked to death with a machete during the Broadwater Farm riots in 1985.
Winston Silcott, along with two other men, was found guilty of his murder but in 1991 their convictions were overturned on appeal because of “unsafe” police evidence.
Pc Ian Broadhurst, 34, of West Yorkshire Police, was murdered by David Bieber, 38, in Leeds on Boxing Day 2003. Bieber also shot two of Pc Broadhurst’s colleagues.
The American bodybuilder, who was wanted by the FBI for ordering two killings in Florida, was subsequently jailed for life.
Detective Constable Michael Swindells, 44, died after he was knifed in the stomach as he and colleagues conducted a search in Birmingham in May 2004.
Detective Constable Stephen Oake died during a police raid on a flat in Crumpsall, Manchester, in January 2003.
Kamel Bourgass launched a frenzied knife attack on the Special Branch officer as he tried to escape. The Algerian was sentenced to life for his murder.
Det Con Oake’s bravery not only saved the lives of several colleagues but potentially hundreds of people who Bourgass was plotting to kill with the poison ricin.
Pc Alison Armitage, 29, was run down by a stolen car in March 2001. She died during an undercover operation in Hollinwood, near Oldham, Greater Manchester. She was run over twice by a driver in a stolen vehicle in the car park of a derelict pub.
In October 1997, Pc Nina Mackay was stabbed to death in a raid in Stratford, east London, by paranoid schizophrenic Magdi Elgizouli.
Police officers also find themselves in danger when they are off duty. Father-of-two Pc Ian Dibell, 41, was off work with a hand injury when he was killed near his home in Clacton in July 2012.
He had gone to help a member of the public who had been injured in a gun attack and was shot himself.