  Experimental evidence from both spin-valve and quantum transport measurements
points towards unexpectedly fast spin relaxation in graphene. We report
magnetotransport studies of epitaxial graphene on SiC in a vector magnetic
field showing that spin relaxation, detected using weak-localisation analysis,
is suppressed by an in-plane magnetic field, $B_{\parallel}$, and thereby
proving that it is caused at least in part by spinful scatterers. A
non-monotonic dependence of effective decoherence rate on $B_{\parallel}$
reveals the intricate role of scatterers' spin dynamics in forming the
interference correction to conductivity, an effect that has gone unnoticed in
earlier weak localisation studies
