City of London Police say anyone with information should call 020 7601 2222, or Crimestoppers, anonymously, on 0800 555 111.
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A 24-year-old man has been arrested on suspicion of murder after the body washed up on the Thames shoreline.
Seven people have now been arrested after a man died from serious head injuries
The 38-year-old officer was on his way home from a night shift when he collapsed. His death is not being treated as suspicious.