The collection consists predominantly of the political, family and personal correspondence of leading members of the Bentinck and Cavendish-Bentinck families and their Cavendish (Pw1), Harley (Pw2 Hy) and Holles (Pw2) forebears.
Further information about the family members and details of their papers can be found under the references for the various sub-groups:
Hans William Bentinck, 1st Earl of Portland (Pw A);
Henry Bentinck, 1st Duke of Portland (Pw B);
William Bentinck, 2nd Duke of Portland (Pw D);
Margaret, Duchess of Portland (Pw E);
William Cavendish-Bentinck, 3rd Duke of Portland (Pw F);
Dorothy, Duchess of Portland (Pw G);
Henry Cavendish-Scott-Bentinck, 4th Duke of Portland (Pw H);
Lord William Bentinck (Pw J); and
William Cavendish-Bentinck-Scott, 5th Duke of Portland (Pw K).
The collection also includes smaller groups of private papers of:
Lord George Bentinck (Pw L);
G.A.F. Cavendish-Bentinck (Pw M);
Charlotte, Viscountess Ossington (Pw N);
John Achard (Pw C).
A significant part of the collection is the Portland Literary Papers (Pw V).