Up until last week all 18 journalists arrested by Elveden were connected to The Sun and targeted as a result of the actions of News Corp's own Management and Standards Committee.
Last Wednesday saw the arrest of 37-year-old Grieg Box Turnbull who left the Mirror after eight years in March but who still freelanced for the paper. A 46-year-old prison worker and a 50-year-old woman were also arrested.
The arrest, on suspicion of breaching the Prevention of Corruption Act 1906, did not appear to have directly stemmed from an MSC tip-off. But it may have come about as a spin-off from inquiries set in train by the MSC.
One well placed Fleet Street source told Press Gazette that there were likely to be many nervous national press journalists at present because, prior to Elveden and last year's Bribery Act, there was no universal understanding on Fleet Street that paying public officials for stories was illegal.
The source said: 'Whistleblowers phone up national newspapers with stories and they generally want paying for them. Most journalists would have realised it was wrong to pay policemen, but not prison officers and other public employees. The fear is that this latest arrest could lead to more dominoes falling."
In written evidence to the Leveson Inquiry, former Mirror editor Richard Wallace said: 'On occasion we have paid public sector employees (connected with the health and prison services) for information".
The Elveden Inquiry has seen most arrests made under the obscure and previously little-used 1906 Prevention of Corruption Act. The act was previously barely mentioned in journalists' media law bible MacNae's and it is not something the PCC Editors' Code covers.
This story first appeared in last Thursday's Press Gazette – Journalism Weekly, a free digital magazine.