Ian Burrell: Dark clouds gathered over Murdoch mean storms for The Thunderer

When they closed the News of the World, the Murdochs tried to create a firewall around the other brands

Once it was a story about hacking mobile phones. But the scandal over British media malpractices has spread to include illicit payments to police and now the hacking of email accounts. And, as this portfolio of "dark arts" has grown, so has the list of News International titles tarnished by their use.

Despite the determined efforts of Rupert Murdoch's company and its army of in-house and recently contracted spin doctors, the focus of the multi-headed investigation into Fleet Street misbehaviour has switched to The Sun and to The Times, the editors of which have been summoned back by Lord Justice Leveson to give further evidence to his public inquiry next week.

At the same time, Scotland Yard is probing the activities of reporters from both The Sun (four more Sun staff were arrested on Saturday, bringing the total to six) and The Times.

"Hacking Inquiry Widens to Times of London", reported the New York Times yesterday, as the Metropolitan Police confirmed it was investigating the 227-year-old title, the famous Thunderer, which once carried WH Russell's dispatches from the Crimea and was known as Britain's paper of record, for allegedly hacking into the private email account of a serving police officer.

The editor, James Harding, faces difficult questions over what he knew of email hacking. Apparently rattled by developments in London, Rupert Murdoch yesterday tweeted criticisms at the Financial Times editor Lionel Barber. When the Murdochs ordered the closure of the News of the World in July they hoped to create a protective firewall that would shield News International's other brands. And at the outset of the Leveson Inquiry there was a feeling within Fleet Street that the process could see other news groups dragged into the mire. That has happened to only a limited degree. The story has infected other newspaper titles – but those within the Murdoch stable.