The Anti-Terrorist Branch of the Metropolitan Police Service said Tuesday it had arrested two men for allegedly intercepting phone calls made to and from members of staff in Prince Charles’ household.

The two men, one of whom is believed to be News of the World journalist Clive Goodman, were arrested in a dawn raid in south London on Tuesday. A third man was also arrested later in the day but has since been released on bail pending further enquiries.

The probe was sparked by complaints from three people within the Royal Household. But police have now widened their investigation beyond members of Clarence House to include other public figures which may have had their telephone calls intercepted.

Ollie Whitehouse, a specialist in mobile technologies at security firm Symantec, said there are three possible avenues of attack if the interceptions were carried out against mobile phones.

“If the attack was carrier out in collaboration with someone working inside an operator, it would be relatively easy to get access to the voicemail platform.

“But if the attack was external, the phone number of the relative voicemail box would be required as well as the PIN number to access the mailbox. It could be possible for someone determined enough to brute force the PIN, or it would not surprise me if there are tools available to carry out such a task. Some operators may even have default PIN numbers,” Whitehouse said.

When a mobile user makes a call to their voicemail box, they are actually dialling a unique number different to their own mobile number. Whitehouse explained that in some cases, if the phone call appears to originate from the mobile number registered to the relevant mailbox, the user may not be required to input a PIN.

“Hackers have proved that spoofing tools can be used to make VoIP calls appear to come from any number,” Whitehouse said.

The Met believes repeated security breaches within telephone networks have taken place over a “significant period of time”.

Reports on the BBC website suggest the alleged interceptions were realised entirely by chance, when a private phone conversation between ITV News journalist Tom Bradby and a Clarence House official allegedly formed the basis of a News of the World article.

Clarence House said it would not comment on the matter.