The brother-in-law of the pest controller poisoned with cyanide in Feltham is the second person to be arrested in connection to his death.
Varinda Singh, 54, husband of Lakhvinder Cheema's sister, was yesterday arrested at home in Windsor on suspicion of murder and attempted murder.
Mr Cheema's fiance Gurjeeta Kaur, 21, remains critically ill in West Middlesex Hospital after eating the same meal at Mr Cheema's Princes Road home.
Lakhver Kaur, 39, Mr Cheema's Ex, was also arrested after the suspected case of cyanide poisoning.
A post mortem conducted on Thursday at Fulham Mortuary was inconclusive with police awaiting results of further toxicology reports.
Police are asking anyone with information to call the incident room on 0208 247 7821 or Crimestoppers on 0800 555 111.