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In page John of Gaunt:

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A later proviso to the legitimation of the Beaufort children was that they were specifically barred from inheriting the throne—the phrase excepta regali dignitate ("except royal status")—was inserted with dubious authority by their half-brother Henry IV.[citation needed] However, as historian and author Nathen Amin points out there was no parliamentary ratification of this scribbled in amendment. Further testing and analysis on these three words is required to determine when exactly they were added. There is every possibility they were added as a later proviso during the height of the Wars of the Roses as a means to discredit any heirs of Margaret Beaufort.