Peter Foster, 36, was on suicide watch.
But his body was discovered during a 3am check by prison officers. Ex-detective constable Foster is the third inmate in less than a MONTH to commit suicide at Lewes jail, East Sussex.
And Prison Service chiefs will probe whether the deaths are linked. Foster killed Det Con Heather Cooper, 33, last October in front of their children Joshua, three, and baby Isabel.
He battered Heather over the head with a baseball bat before stabbing her in the throat at the couple’s home in Haslemere, Surrey.
He was given 17 years after dumping her body in woods. Fellow Lewes inmate Nathan Vaughan-Jones, who knifed his domineering stepfather to death, was found hanged on Friday.
The 34-year-old lag had a history of depression but was not considered a suicide risk. Sex offender Colin Morton was also discovered hanged on July 1.