There are three different types of dissertation fellowships, with names reflecting the source of funding for the fellowship.
There may be some exceptions to this rule, but not many. This is related to factors beyond the scope of this post, but one factor which also helps is the wealth of archival material that we have in Europe.
Graduate students who have presented a poster are eligible for the dissertation session in a subsequent year, but may present a poster session only once during their graduate career.
We give about 10 full scholarships per year, and more students come in with external funding.
I myself work with Tim Besley and other co-authors on matters related to economic history. The website eh.
Viva voce examinations are not normally held but are required if there is a possibility of failure and can also be held if an examiner feels that there is some peculiarity about the dissertation which can best be explored by questioning the candidate.
This includes references you cite.