[4] In 1793, he was promoted major-general, and was appointed colonel of the newly formed 81st Regiment of Foot on 19 September with instructions to recruit volunteers for it.

In 1804, the Duke of York recommended him for the colonelcy of the 77th Regiment of Foot, then part of the Indian establishment, noting that "the difference of emolument is of great consequence" to Bertie.

[3] Bertie retired from active service in 1809 upon inheriting the title of Earl of Lindsey from his third cousin on 8 February 1809.

[3] The earldom had been held by Robert Bertie, 1st Marquess of Lindsey from 1706 until 1715 when he was he was created the 1st Duke of Ancaster and Kesteven.

[1] In 1801, he was nominated as Member of Parliament for Stamford, where the Bertie family had once held an electoral interest, by the Marquess of Exeter, then pre-eminent in the borough.

[5] Through his daughter, Lady Charlotte,[6] he was a grandfather of Charlotte Maria Guest (wife of Richard Du Cane); Ivor Bertie Guest, 1st Baron Wimborne (who married Lady Cornelia Henrietta Maria Spencer-Churchill, a daughter of John Spencer-Churchill, 7th Duke of Marlborough);[7] Katharine Gwladys Guest (wife of the Rev.