The question of the uniqueness of a certain combinatorial structure has arisen in three contexts: a) is the regular near octagon with parameters

unique [5]? b) is the partial

-geometry with nexus three and blocksize

unique [2]? c) is there a unique graph such that it is the graph of a parallelism of

with respect to any [1]? We observe that these questions are equivalent and give an affirmative answer. In fact, we prove a more general theorem, showing the truth of a conjecture by Cameron.