Schematic of the steps that compose a single accretion episode. The vector schemes in the upper part of the figure represent the initial and final configurations of the angular momenta, in a case similar to the one shown in Fig. lb by King et al. (2005). Left: an accretion disc settles around the BH, in a misaligned configuration. Centre: a warp develops, and the innermost part is forced to rotate in the BH equatorial plane and either co- or counter-align. Right: the BH spin changes in magnitude when gas is accreted at the innermost stable orbit.