Betty Brown, believed to be the oldest surviving victim of the Post Office Horizon IT scandal at 93 years old, was presented with an OBE at Windsor Castle on Tuesday.
The County Durham woman was among 68 individuals honoured by the King during the investiture ceremony, which also saw Luther actor Sir Idris Elba and ice skating legends Dame Jayne Torvill and Sir Christopher Dean receive recognition.
Ms Brown was awarded the Officer of the Order of the British Empire for her services to justice, following years of campaigning on behalf of subpostmasters affected by the faulty Horizon accounting system.
Speaking after the ceremony, she described the recognition as "a great honour that the King has recognised an ordinary person trying to do something good in the community."
A Post Office Horizon victim, 93, has spoken out after receiving an OBE from the King, but 'not a penny' in compensation
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Together with her late husband Oswall, Ms Brown operated the Annfield Plain Post Office near Stanley from 1985 until 2003.
During that period, the couple estimate they paid approximately £100,000 from their personal savings to cover shortfalls that never actually existed.
The discrepancies were caused by the Horizon accounting system, developed by Japanese technology company Fujitsu, which falsely indicated that funds were missing from branch accounts.
The flawed software sits at the heart of one of Britain's most significant miscarriages of justice, resulting in roughly 1,000 wrongful prosecutions and convictions between 1999 and 2015.
Betty and Oswall Brown paid £100,000 from their savings to cover non-existent shortfalls
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Ms Brown was among the original group of victims who pursued legal action against the Post Office in proceedings led by Sir Alan Bates.
Following her meeting with Charles, Ms Brown said the monarch was "fully informed" about the scandal and its impact on victims.
She revealed that the King shares the frustration felt by those affected, stating: "He is as upset about it as we are."
Ms Brown used the opportunity to deliver a pointed message, urging the King to convey her concerns to Government ministers.
Betty Brown lowering into a curtsy in front of King Charles
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"What I've said to him was: 'Impress on the Prime Minister that there is no price on justice.' The quibbling about the money, stop it, and finish Horizon immediately," she said.
She also told the King that "justice is more than money" and asked him to relay this to Sir Keir Starmer and his cabinet.
When asked about the monarch's reaction, Ms Brown confirmed: "He took it on board."
Ms Brown issued a direct plea to the Prime Minister, asking him to resolve the scandal "as quickly as you can."
Betty Brown was particularly critical of Fujitsu's approach to affected families
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"Don't take another 26 years, because all you're doing is waiting for the poor souls to die off, one-by-one, until there will be no one left and the case is forgotten about in the history books, if it ever makes it," she warned.
Despite settling on the Government's redress scheme late last year, Ms Brown said she has not yet received "a penny" in compensation.
She was particularly critical of Fujitsu's approach to affected families, saying: "We don't want therapy, we want money to put a roof over their heads and give them what Horizon took away from us."
Asked about her decades-long fight for justice, Ms Brown attributed her resilience to honesty: "The longer you tell the truth, the stronger the truth gets."