The partner of Gillian Astbury, who died after slipping into a diabetic coma at the scandal-hit Stafford Hospital in 2007, told ITV News the criminal investigation into her death "has been a long-time coming".
Ron Street said what happened at the hospital was due to "several years of complacent mismanagement":
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He said people have handed over thousands of pounds in good faith, only to find the advert has nothing to do with Mr Lewis or his company.
The memorial service will be attended by Prince Harry and Meghan Markle.
David Browning admits manslaughter by diminished responsibility but denies murder.