Question: Which British peer and politician born in 1734 was a great-grandson of the 1st Duke of Marlborough?
Sentence (from "Earl Spencer (peerage)"): Previously, he had been created Viscount Spencer, of Althorp in the County of Northampton, and Baron Spencer of Althorp, of Althorp in the County of Northampton, on 3 April 1761.
Relevant evidence: No