Mrs Wardell, 38, was found dumped by the roadside near Nuneaton, Warwickshire, on Monday after being forced to help a gang which robbed the town's building society where she worked.
Gordon Wardell, 40, returned home on Sunday night to the couple's home in nearby Meriden, West Midlands, to find a man in a clown mask holding a knife to his wife's throat.
Yesterday he said: 'I am still trying to come to terms with the situation. . .she was the best, so conscientious.'
He confirmed that at the age of 17 he had been jailed for four years for stabbing the wife of his school science master. He denied a charge of attempted murder but pleaded guilty to grievous bodily harm.
When asked by journalists if he told police about this conviction, he said: 'As soon as I was asked about it I told them. I was open about it.'
He described how he had been attacked in his home by members of the gang. 'I was grabbed from both sides and forced down. They told me to keep quiet and do what I was told and get down on the floor. The next thing I knew I was on the floor, bound and gagged.'
A reward for information leading to the capture of the killers reached pounds 50,000 when the Daily Mirror matched a pounds 25,000 sum offered by the Woolwich Building Society, from whom the robbers stole about pounds 15,000.
Police believe the gang of at least three held the couple hostage overnight at their home before driving Mrs Wardell to the building society where she was forced to unlock the doors and switch off the alarms. She was then murdered.
Witnesses should contact the police on 0926 415760.