  We consider the phase equilibria of a fluid confined in a deep capillary
groove of width $L$ with identical side walls and a bottom made of a different
material. All walls are completely wet by the liquid. Using density functional
theory and interfacial models, we show that the meniscus separating liquid and
gas phases at two phase capillary-coexistence meets the bottom capped end of
the groove at a capillary contact angle $\theta^{\rm cap}(L)$ which depends on
the difference between the Hamaker constants. If the bottom wall has a weaker
wall-fluid attraction than the side walls, then $\theta^{\rm cap}>0$ even
though all the isolated walls are themselves completely wet. This alters the
capillary condensation transition which is now first-order; this would be
continuous in a capped capillary made wholly of either type of material. We
show that the capillary contact angle $\theta^{\rm cap}(L)$ vanishes in two
limits, corresponding to different capillary wetting transitions. These occur
as the width i) becomes macroscopically large, and ii) is reduced to a
microscopic value determined by the difference in Hamaker constants. This
second wetting transition is characterised by large scale fluctuations and
essential critical singularities arising from marginal interfacial
interactions.
