Once I Was A Clever Boy comes this detail about Mary's exhumation from Peterborough Cathedral and re-burial in Westminster Abbey:
In 1603 Queen Mary's son, now King James I of England, sent Garter King of Arms with a pall decorated with Mary's arms to place on her tomb. A new tomb for her in Westminster Abbey was commissioned in 1606 from Cornelius Cure and, following his death the next year completed by his son William.
Finally on October 11th 1612 came exhumation from Peterborough. A modern plaque and the Royal and national flags of Scotland today mark the site of the grave. Queen Mary's remains were taken for reburial at Westminster in the south aisle of King Henry VII's Chapel, opposite Queen Elizabeth I. who lies in the north one. Queen Mary I had planned to rebury her mother Queen Katherine at Westminster and provided for a joint tomb in her will in 1558, but that plan was never carried out. Queen Elizabeth I did nothing to recover the body of her own mother from its ignominious grave in the Tower of London. King James may have had no personal memory of his mother - they were seperated when he was only a few months old, but in death he honoured her, and perhaps by burying her at Westminster implied not merely that she had given him his title to the English throne, but that she was herself its rightful occupant.