  The main objective of this paper is to explore abundances of fluorine in hot
Extreme Helium Stars (EHes). Overabundance of fluorine is a characteristic
feature for cool EHes and R Coronae Borealis (RCB) stars and further enforces
their close connection. For hot EHes this relationship with the cooler EHes,
based on their fluorine abundance is unexplored. We present in this paper the
first abundance estimates of fluorine determined from singly ionised fluorine
lines (F\,{\sc ii}) for 10 hot EHe stars from optical spectra. Fluorine
abundances were determined using the F\,{\sc ii} lines in two windows centered
at 3505 \AA \ and 3850 \AA . Six of the 10 stars show significant enhancement
of fluorine similar to the cool EHes. Two carbon-poor hot EHes show no
signature of fluorine and have a significant low upper limit for the F
abundance. These fluorine abundances are compared with the other elemental
abundances observed in these stars which provide an idea about the formation
and evolution of these stars. The trends of fluorine with C, O, and Ne show
that significant helium burning after a CO-He white dwarf merger can account
for a majority of the observed abundances. Predictions from simulations of
white dwarf mergers are discussed in light of the observed abundances.
