  T. De Medts, Y. Segev and K. Tent [Special Moufang sets, their root groups
and their \mu-maps, Proc. Lond. Math. Soc. (3) 96 (2008), 767-791] proved that
the little projective group of a special Moufang set M(U,\tau) is perfect
provided that U has size at least 4. We give a short, elementary and
self-contained argument, working with Timmesfeld's concept of special
(abstract) rank one groups with arbitrary unipotent subgroups [Abstract root
subgroups and simple groups of Lie type, Monographs in Mathematics, 95.
Birkh\"auser, 2001].
