After leaving Harrow, Herbert was appointed an ensign in the 12th Regiment of Foot in 1775 and travelled the continent over the next five years, visiting France, Austria, Eastern Europe, Russia and Italy with Rev.

At the start of the French Revolutionary Wars, Herbert saw action in Flanders, where he commanded the 2nd and 3rd Dragoon Guards and liaised with Prussian and Austrian forces.

At the general election of 1780, Herbert became Member of Parliament for the family borough of Wilton and sided with the Whig opposition.

He held the seat for Wilton again from 1788 to 1794, the year he inherited his father's titles and estate and also succeeded him as Lord Lieutenant of Wiltshire.

Their children included: His second marriage was on 25 January 1808 to Countess Catherine Semyonovna Vorontsova, a daughter of the prominent Russian aristocrat and diplomat Semyon Romanovich Vorontsov.