It relies on the duchy to provide it with accurate information without carrying out its own independent checks.
As heir apparent, William would also become the Duke of Cornwall, and receive the annual revenues from the duchy of Cornwall.
He will also lose the massive income from the lands held by the duchy of Cornwall, which currently provide some of their funding.
Well, the Prince last year received an annual income from the duchy of £19m, on which he paid £4.4m in income tax and VAT.
It also criticised the lack of official scrutiny of the duchy's account.
Baron Conon must wait, therefore, perhaps until the present elderly duke is dead and the duchy falls under feeble heirs.
But certainly, the son of Dwerostel would have no word in the control of the duchy.
The third crown-land of Bohemia is the duchy of Silesia, with an area of 1,987 square miles.
And here was a certainty of tolls and taxes, which would enrich the duchy.
The collections of the Abbé, as may be anticipated, are of great value; they relate almost wholly to the history of the duchy.