A lawyer for the police said he was worried about "sensationalising" the inquest with a live demonstration of the bag and offers a video clip by an expert as alternative.
Police reveal "problems in the DNA analysis" of mixed profile found on Williams' hand - found the contamination was from scientist at scene.
The error was spotted by a scientist who's evidence helped convict the killers of Stephen Lawrence in January. The coroner wants to hear from her.
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In a wide-ranging Peston on Sunday interview, he said Parliament security needs reviewing and the PM's counter-terror strategy is flawed.
The terror attack carried out by Khalid Masood at Westminster that left four people dead lasted less than two minutes say police.
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.