A Mediterranean couple sought in connection with Williams' death is now considered a "red herring" after further police inquiries.
Organisers of the ladies fashion course Williams' enrolled on in secret will give statements to the inquest too.
The lawyer for MI6 says calling corporate witnesses will "paint a picture and set the scene".
Two experts have tried to reconstruct how Mr Williams could have got into the bag and locked it - The coroner says he wants a live demonstration in court.
The issue of whether or not Mr Williams could have got into the bag and padlocked it from the inside "goes to heart" of inquest the coroner says.
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The 20-year-old was found fatally wounded on Roth Walk, near Finsbury Park, north London at around 3am on Saturday, Scotland Yard said.
Police have arrested a man wanted in connection with a burglary at the home of pensioner Richard Osborn-Brooks.
The rally comes after it emerged that the Home Office destroyed thousands of landing cards documenting the arrival of windrush-era migrants