The number of people believed to have a motive for the killing continues to grow, however. And the investigation has uncovered a hidden community that appears happy to police itself rather than attract the spotlight of publicity.
The murder of Tarsem Singh Purewal, 60, as he left his newspaper's offices in Southall at 8.20pm on 27 January has exposed Britain's million-strong Sikh community to unwanted attention. The best-selling Punjabi language newspaper Des Pardes, owned and run by Mr Purewal, has also come under scrutiny.
After translating the past three months' editions of the weekly tabloid in the search for clues to a motive, the police have discovered the newspaper - considered the Punjabi version of the News of the World - regularly names adulterers, rapists, allegedfraudulent businessmen and child abusers.
But the newspaper, selling about 10,000 copies nationally, allegedly breaks the law by naming rape victims. The police believe about ten people are attempting to sue Des Pardes over its coverage.
Remarkably, the paper's actions and reputation had remained a secret known only to Punjabi speakers. Gurbuksh Singh Virk, the new editor, yesterday denied breaking the law and said he was not aware of any outstanding legal actions.
Nevertheless, the police are adamant that they have found examples. Det Supt Colin Hardingham, heading the inquiry, said: "Some reports are based on court cases, others appear to be just accusations. The paper appears to thrive on scandals. People who have had affairs are named, along with claims of dodgy business practices."
He added: "The community leaders have been extremely helpful, but part of the problem is getting hard facts - most things seem to run on rumour and speculation."
Men are named more often than women in the adultery cases. The consequences are dire. Harbans Singh Anand, an Ealing borough councillor and adviser to the Indian Workers' Association, explained: "The person is instantly isolated. People will just ignore them because of the disgrace. The family can also suffer great shame. Mr Purewal was well known for publishing details of affairs...he was a very inde- pendent man who wanted to expose the shortcomings in society."
Until now most complaints involving personal and private matters were taken to Sikh community leaders who act as mediators and help to avoid greater publicity. A three-tier caste system has also maintained discipline, possibly preventing some from speaking out.
Chief Inspector Gordon Cuthburton, community liaison officer for Ealing, said: "The Sikh population sees this as part and parcel of their community. Southall is still seen as a community within a community, a self-contained unit unaffected by the surrounding areas. It's very close-knit, especially when it comes to issues such as adultery."
A stroll down the High Street reveals how different the district is. Almost every shop is Asian, windows piled high with brilliantly coloured sweets, rolls of brightly coloured cloth, exotic fruits and Halal meats.
The circumstances in which Mr Purewal was murdered have spawned theories. His killing was a textbook hit. He died instantly from a single bullet, probably from a shotgun, fired inches from his heart. So far, the police have not found a witness, a murder weapon or a cartridge case. The killer would have been covered in blood - the body practically exploded, spraying blood 2ft into the air.
Nothing was taken from the body or offices, ruling out an armed robbery. The latest theory is revenge by a Sikh group fighting for a separate Khalistan in the Punjab, in India.
About three weeks ago, Des Pardes carried an article claiming the International Sikh Youth Federation (RODE faction), was keeping funds raised at British Sikh temples rather than passing them on to the independence movement. The ISYF was apparently furious. Mention of the organisation to several leading members of the Sikh community brings requests for anonymity and mutterings of danger.
Des Pardes staff suggest a professional hit squad was sent by the Indian government, angered at the paper's sympathetic coverage of the fight for independence. Alternatively, Mr Purewal may have fallen out with business partners.
Det Supt Hardingham concluded: "Twelve years ago this murder would have caused the community to erupt. Now it ends up in political debate.
"We are getting tremendous support from the community but the rumour machine keeps churning out potential suspects rather than facts."Reuse content