In 1406 a thief was bold enough to steal from the royal treasure itself – and as far as we know get away with it.

In Easter term 1408, the Middlesex coroner John Lilleston submitted a membrane to the court of King’s Bench with seven cases from the previous year. One of these was a sanctuary seeker: Gregory Hannam had sought asylum in the church of St. Mary le Strand just before Christmas 1407. There Hannam confessed to Lilleston what seems like a bold crime: around the beginning of November 1406 he and other felons had broken into the cellar of the king’s palace at Westminster at night. They stole from the king four coffers, eleven pieces of silver, and a good deal of other plate (detailed in the record).
Although King Henry IV was evidently very displeased by this – soon after, he complained that despite having committed many felonies and outrages Hannam and his accomplices were able with impunity to “wander about in divers counties of the realm” – Hannam appears to have escaped arrest. In September 1407, Hannam committed another burglary: he and accomplices broke into the vicarage at Stepney and stole a missal, a breviary, two scarlet hoods, and other goods and money from the vicar, altogether worth 17 marks (roughly £10).
Something in December 1407 prompted Hannam to dash into the Strand church, where the coroner recorded his confession and noted that he had ordered the constable and townspeople of Westminster (under whose jurisdiction the Strand church fell) to guard him so he would not escape.
But there is no record of abjuration, and nothing that I can find in any other record indicates what happened to Hannam. Although normally coroner’s records were filed at King’s Bench because there was some further process against the felon there – an outlawry, a trial – this record may have ended up in the King’s Bench indictment files by accident, as it was written on the same membrane as another case that did end up in court (KB29/49, m.16).
So Hannam may have abjured (the coroner just not recording it); or perhaps the coroner’s note that he had commanded the townspeople to guard Hannam was a backhanded way of admitting that the felon ran away after making his confession. Another case at the same church did end up with such an escape… read about that here.
TNA, KB 9/195/2, m.25; CPR 1405-08, 308.