Likely apocryphal. It isn't in the massive official "Despatches of Field Marshal the Duke of Wellington" and the exaggerated, humorous style is not characteristic.

• morsch

  today at 8:55 PM

  Thanks, I read through a few pages and found it a more interesting read than the original link.

  E.g. here he's complaining to the undersecretary of state:

  https://archive.org/details/dispatchesoffiel10welluoft/page/...

  Here (and a few lines on the page before) is a long letter with his advice on how to reconstitute the (allied) government of Spain:

  https://archive.org/details/dispatchesoffiel10welluoft/page/...

Entertaining if fictive. His comments to his army and his own role in the victory are I hope better attested to.

Why would Wellington have to answer to the Foreign Office for the administration of the forces under his command when that was the responsibility of the War Office?

Technically from Sir Arthur Wellesley, he wasn't made duke until 1814.

There's no way that's not a joke written many decades or more later.