Overwhelmingly by inheritance he was rendered a sterling millionaire, a threshold reached by his own death estate which is estimated to apply to seven other British residents per year, only, in 1905.

Apart from his political career Cowper held the position of Lord Lieutenant of Bedfordshire between 1861 and 1905.

In 1871, Cowper managed to obtain a reversal of the attainder of the Scottish lordship of Dingwall and the English barony of Butler, which had been under attainder since 1715, and he became the 4th Lord Dingwall and the 3rd Baron Butler as well.

He came to own more than £1M of assets which Sir Leo Chiozza Money, an analyst of the rich of the era, estimated was true of only eight British people who died "in an average year".

He was succeeded in the barony of Lucas of Crudwell and the lordship of Dingwall by his nephew, Auberon.