  Steady state accretion discs larger than ~ 0.01-0.1 pc are known to be
gravitationally unstable for the accretion rates needed to explain
super-massive black hole (SMBH) activity. We propose that SMBH are fed by a
succession of mass deposition events with randomly directed angular momenta.
Because of incomplete angular momentum cancellation a warped accretion disc
forms in the inner few parsec. The orientation of the disc performs a random
walk. Deposition of new material promotes SMBH accretion at rates much faster
than viscous. Observational implications of this picture include: (i) lighter
accretion discs that can fuel AGN and quasars and yet avoid star formation at R
>> 0.1 pc; (ii) star formation inside the disc is not a function of mass
accretion rate only. It can take place at high or low accretion rates, e.g.,
when too few clouds arrive in the inner region. An example of this might be the
central parsec of our Galaxy. (iii) The discs can form Compton-thick obscuring
structures of ~ parsec size as required in AGN unification models; (iv) faster
black hole growth resulting from misalignment of the disc and the black hole
spin in the early Universe; (v) Isotropic deposition of SMBH energy and
momentum feedback in the galaxy bulge. This may help explain the high
efficiency with which it seems to be operating in the Universe. (vi) No
correlation between SMBH activity and the presence of kiloparsec scale bars or
gaseous discs in galactic bulges; (vii) Bodily collisions between gaseous
components of merging galaxies facilitate production of gas streams feeding the
centre of the combined galaxy. Mergers should thus be catalysts of SMBH growth.
(viii) Conversely, galaxies experiencing fewer mergers are more likely to form
massive nuclear star clusters than feed their SMBHs.
