  We discuss a realisation of the pentaquark structure proposed by Jaffe and
Wilczek within a simple quark model with colour-spin contact interactions and
coloured harmonic confinement, which accurately describes the $\Delta-N$
splitting. In this model spatially compact diquarks are formed in the
pentaquark but no such compact object exists in the nucleon. The colour-spin
attraction brings the Jaffe-Wilczek-like state down to a low mass, compatible
with the experimental observation and below that of the naive ground state with
all $S$-waves. We find, however, that although these trends are maintained, the
extreme effects observed do not survive the required ``smearing'' of the delta
function contact interaction. We also demonstrate the weakness of the
``schematic'' approximation when applied to a system containing a $P$-wave. An
estimate of the anti-charmed pentaquark mass is made which is in line with the
Jaffe-Wilczek prediction and significantly less than the value reported by the
H1 collaboration.
