Lynn Harvey's husband Phil died in October 2010 following complications from a triple heart bypass operation in September 2009 at Basildon Hospital's cardio unit.
Mrs Harvey claims that her husband caught an infection in his leg following the operation, and has criticised the treatment he received as being blase and hampered by unneccessary delay.
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The mayor claimed last week the bridge would cost more to cancel than to build. He said £37.7m of public money had already been spent.
The houseboat in Chelsea, west London, comes complete with three bedrooms, three bathrooms, a reception room and its own patio.
The city is one of a small number which has seen an increase in traces of the Class A substance over recent years.