He ploughed a rented car through a crowd of pedestrians on Westminster Bridge before launching an attack on the officer stationed at the gates to the Palace of Westminster on March 22 last year.
Masood fatally injured four people in just 30 seconds before running towards 48-year-old PC Palmer armed with two knives.
The inquest into their deaths today heard the terrorist's 4×4 was as "lethal as a knife or gun" as the Palace of Westminster's security system "completely failed" and had not "functioned for years".
Armed officers were in place outside the Houses of Parliament but too far away to protect PC Palmer.
Earlier in the inquest the court was told there had been a change of tactics from having armed guards in fixed positions at the gates to using patrolling firearms officers.