Four suspects have so far been identified by police investigating possible criminal charges in the Post Office scandal, Sky News has learned.
Sources have said that among the offences being considered are perverting the course of justice and perjury.
Hundreds of sub-postmasters were wrongly prosecuted for stealing from their branches between 1999 and 2015 after faulty Horizon software caused accounting errors.
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The Metropolitan Police is a so-called core participant in the Post Office public inquiry and has been monitoring and assessing material submitted.
It is expected that the number of suspects being investigated by police could rise in the next six to 12 months.
More than a million documents are believed to be being sifted through and the number of police officers investigating the scandal has also risen from 80 to 100, with work across every single police force.
It is not expected, however, that any charges will be brought before 2027/28, and that time frame could be extended.
A Sky News source said the number of suspects was seemingly “just a starting point”.
A meeting took place this weekend between more than 150 sub-postmasters, including Sir Alan Bates, and the Metropolitan Police.
Sir Alan said he had been told by officers that “it was going to take a few years” and that there are “no restrictions on how high investigations will take them”.
He also said the priority for sub-postmasters was financial redress and then, after that, victims will be “looking for people to be held to account”.
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A Metropolitan police spokesperson said: “Yesterday [17 November] we met with Alan Bates and some of the affected sub-postmasters to provide a brief on our progress and next steps.
“Our investigation team, comprising around 100 officers from forces across the UK, is now in place and we will be sharing further details in due course.
“Initially four suspects have been identified and we anticipate this number to grow as the investigation progresses.”