An inquest into the people who lost their lives in the Westminster Bridge terror attack will begin later this year.
Families of victims have called for it to examine the continuing "failure" to get to grips with radicalisation on the internet and in prisons.
American tourist Kurt Cochran, 54, retired window cleaner Leslie Rhodes, 75, DLD College staff member Aysha Frade , 44, and Romanian tourist Andreea Cristea, 31, died when Kent-born Khalid Masood, drove his car at them on Westminster Bridge on March 22.
Masood, 52, then fatally stabbed PC Keith Palmer , 48, in the Palace of Westminster's forecourt before he was shot dead by police.
Gareth Patterson QC, representing the families, stressed the importance of getting to the bottom of issues surrounding the death of the police officer, examining security arrangements and precautions at Parliament, and PC Palmer's body armour.
The inquests begin on September 10 and are expected to last four weeks; they will be followed immediately by a separate jury inquest into the death of Masood.
The pre-inquest hearing was held at the Old Bailey on Monday (January 15) and conducted by Chief Coroner Mark Lucraft QC.
It was heard that Masood took steroids in the days and hours before the attack.
Mr Patterson QC called for the coroner to examine the problems that are highlighted in "terrorist trial after terrorist trial" at the Old Bailey.
They included "the internet, end to end encryption, and radicalisation in prison and failure to get to grips with these problems which occur again and again", he said.
Calling on the coroner to shed light on these problems, he said: "Terrorist trial after terrorist trial show the same problems featuring in the evidence."
He went on: "Why is it that radical material continues to be freely available on the internet? We do not understand."
The Westminster Bridge attacker used WhatsApp to see Jihadi material which could not be obtained without the phones, he said.
"We do not understand why it is necessary for WhatsApp and Telegram to have end to end encryption."
And addressing PC Palmer's death, Mr Patterson QC added: "We welcome the indication that you will be investigating further what happened at the Houses of Parliament and how it was this attacker was able to get through those gates and how it was PC Palmer was apparently stationed alone and unarmed with, it seems, inadequate body protection."
The inquest would examine Masood's personal history, how he came to the attention of the authorities, his planning, and movements and dealings with others before the attack.
It would scrutinise the sequence of events on Westminster Bridge and how each of the victims were fatally injured and efforts made to treat them at the scene and in hospital.
Video evidence would include the attack itself as well as footage showing the hiring of the car, the purchase of knives and reconnaissance.
A range of experts would deal with PC Palmer's body armour, a "psychological autopsy" of the killer and toxicology on samples from Masood providing evidence of anabolic steroids in the hours or days before his death.
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