They gathered at Braybrook Street for the service to remember Detective Sergeant Christopher Head, 30, Temporary Detective Constable David Wombwell, 25, and PC Geoffrey Fox, 41, who were killed in the line of duty on Braybrook Street, under the shadow of Wormwood Scrubs prison , in 1966.
Also attending the small service which began at 3pm - shortly before the time the officers were killed - were members of the community and serving officers.
The crime stunned the nation, and became known as the Massacre of Braybrook Street.
Murderers Jack Witney and John Duddy were arrested a short while after, as was arch villain Harry Roberts following a massive manhunt, and the trio were told they would spend a minimum 30 years in prison.
'Gone but never forgotten'
Speaking ahead of the annual service , Hammersmith and Fulham borough commander Chief Superintendent Gideon Springer said: “It is only right and proper that we gather together on this day to remember Detective Sergeant Christopher Head, Temporary Detective Constable David Wombwell, and Police Constable Geoffrey Fox, and the ultimate sacrifice that they made in protecting the people of London.
"They are gone but never forgotten.”
Hammersmith and Fulham Council leader Cllr Stephen Cowan said: “Today we remember these officers for their bravery that led to their lives being cruelly taken while they protected our community.
"In doing so we not only proudly honour those three police officers and their families, we also honour all who serve to keep us safe and out of harm’s way today.”
Deputy Commissioner Craig Mackey, added: “Today’s commemoration of the tragic events from 50 years ago serves as a reminder to us all of the grave dangers police officers face as they go about serving the public.
“Today we stand with the families of the three officers, and join them in remembering and honouring them for their duty. The Metropolitan Police Service will never forget the sacrifice they made.”
Paper boy inspired to join force after seeing headlines
Another person attending was Jim Smith, a police officer based at Limehouse at the time. He helped with the police search on the day.
He said: "We were called into a briefing then came down here to search the area for the car.
"It was a terrible day. It was unbelievable that it ever happened. To drive down here now and think those three men drove down here, saw the car and gave it a pull.
"I was there when Harry Roberts was arrested. That was a good day but what a horrible man. I was disgusted when he was released. He should never be allowed out in the streets."
One unnamed person at the service told getwestlondon they joined the police force after seeing the story on the killings.
"On August 13 1966 I did my first and only paper round and this was front page news," they said.
"Because of that I decided if it was a job worth dying for it was a job worth doing. I ended up being a Met Officer for 30 years."
Ex-police officer copper Brian Robbins said: "I was with the three officers the night before it happened on a social occasion.
"I worked with Geoff Fox a lot of times. He took me under his wing. He could teach you without making you feel small.
"He was a nice nice man. It was a day just like today. It was hot then too, and a Friday."
Ita Ahearn lived close to the scene at the time. She recalled: "It shocked the whole community. It's very sad still; the emotions are all still there."
Also attending the service were Chris Rider and Brian Collett, journalists who reported the incident for the Shepherd’s Bush Gazette at the time.
The service was also the first since the death of Reg Collins who lived on Braybrook Road. He tended the memorial for the fallen officers and would silently pay his respects the men every August 12. Police had fondly dubbed him ‘the man with the white hair’.
What happened in Braybrook Street on August 12 1966?
The plain-clothes officers were on duty as the crew of a police ‘Q car’, call sign ‘Foxtrot One One’, when they approached a Standard Vanguard, registration PGT 726.
Christopher Head and David Wombwell were in the course of questioning the male occupants when they were callously shot by Roberts and an accomplice.
Geoffrey Fox, who had remained in the police car in front following procedures, fell victim to those same men moments later.
Roberts opened fire on the officers when he feared they would discover the firearms his gang was planning to use in an armed robbery. He shot dead two of the officers, while one of his accomplices fatally shot the third.
Following the shootings, Roberts hid in Thorley Wood in Hertfordshire to avoid capture. A £1,000 reward was offered for information leading to his arrest.
Roberts used his military training to evade capture for 96 days. He was finally captured by police while sleeping rough in a barn.
He was convicted of all three murders and sentenced to life imprisonment with a recommended minimum term of 30 years. He served nearly 48 years in prison and was released in January 2015 at the age of 78.
Duddy died in prison in 1981, while Witney was released in 1991 and murdered by a heroin addict in 1999.