Journalist Caroline Criado-Perez has told ITV London that although she welcomes Twitter's new move to report abusive messages, there was more that needed to be done.
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The one-year-old Yorkshire Terrier was attacked and killed while being taken for a walk.
The lifeboat crew carried the pair into their boat and dropped them off back at Tower Bridge as people watched from the riverside.
The huge painting took two graffiti artists thousands of hours to complete in east London.