The court was shown CCTV footage of the killers stalking their target for much of the night before striking outside the Woody Grill kebab shop in Kilburn.
Sabrina Gachette, who sat in court with her mother throughout the trial, said:
Seeing that was scary. How many times did they see us but not once did I see them. They knew there was girls out there.
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A man who met PC Keith Palmer said his murder "sent a shiver down my spine".
Officers were given the touching letter at Brixton Station while they were on a reassurance patrol after yesterday's attack
The 52-year-old had previous convictions for violence but was not on the anti-terror watchlist.