The first creation came on 19 March 1719 (as Baroness Glastonbury), as a life peerage and as a subsidiary title for Ehrengard Melusine von der Schulenburg, Duchess of Kendal and Munster, mistress of George I. The second creation came on 29 October 1797 when the politician James Grenville was made Baron Glastonbury, of Butleigh in the County of Somerset, with remainder, in default of male issue of his own, to his younger brother General Richard Grenville and the heirs male of his body.
The first creation of the title Baron Glastonbury was bestowed on March 19, 1719, for Ehrengard Melusine von der Schulenburg, Duchess of Kendal and Munster, mistress of George I. The second creation occurred on October 29, 1797, when James Grenville became Baron Glastonbury of Butleigh in Somerset, with the remainder passing to his brother General Richard Grenville and the male heirs of his body if he had no sons.