It is understood that the 41- year-old man was arrested early yesterday morning but Warwickshire police have refused to identify the suspect in custody unless and until charges are laid.
The asphyxiated body of Mrs Wardell, 38, was found dumped in a lay-by near Nuneaton on 12 September. It was subsequently discovered that pounds 15,000 in cash and 400 blank building society cheques were missing from the Nuneaton branch of the Woolwich Building Society where she worked.
Mr Wardell, who was later found by detectives at the couple's home in Meriden, near Coventry, told the police that he had returned the previous evening to discover his wife being held at knifepoint by a man wearing a clown's mask.
He said he was tied up by the raiders who then abducted his wife and apparently took her to her branch at about 5am the following morning, where she was forced to disable security alarms and open the safe.
A week later, Mr Wardell, an operations manager for a distribution company, took part in a reconstruction of his movements on the evening before his wife was killed, but this did not yield any significant information or witnesses. Last week, he led more than 200 mourners at his wife's funeral.