I would appreciate hearing from anyone who has information on this officer (particlarly his antecedents) beyond that appearing below.

We have a family picture of Robert Douglas inscribed Capt Robert Douglas Royal[sic]Scots Guards and another of General Douglas.

According to his own will (see below) Robert Douglas was Colonel Commandant in the Royal Regiment of Artillery.

According to Thomas Willan's will (appointing him one of his executors) he was Lieutenant General in the Royal Artillery of Woolwich Warren [Greenwich] Middlesex.

Will of Robert Douglas, Colonel Commandant in the Royal Regiment of Artillery
Date written 18 November 1826
First Codicil Dated 25 December 1826
Date Proved 20 April 1827

In his will he explicitly mentions (and provides for those still living):

Departed children Harriet{?} and Henry{?}
Beloved wife Mary
Daughter Maria Close wife of Major Majorum{?} Close{?}
Son Robert Douglas Captain in the Royal Regiment of Artillery Brevet{?} Major and CB{?}
Son John Kearsley Douglas Esq. of Twyford Abbey and his wife Isabella Maria [née Willan]
Son William Douglas Lt. Col in the Corps of Royal Engineers
Nephew William Moffat Esq. late a Captain in the Honorable East India Company's Naval Service
Granddaughters Christiana Isabella Douglas and Isabella Maria Douglas