I am currently looking at Ronan and Stroth's 1984 paper Minimal Parabolic Geometries for the Sporadic Groups. When considering the $3$-minimal parabolic system of $F_{1}$, they cite a preprint by Buekenhout and Fischer:
F. Buekenhout and B. Fischer, A locally dual polar space for the Monster, preprint.
I have tried finding this preprint without success. Elsewhere, it has been cited as an unpublished manuscript. Does anybody know if this is now in the public domain, and if so where one could obtain a copy of this from.