  We present stellar radial velocity data for the Draco dwarf spheroidal galaxy
obtained using the AF2/WYFFOS instrument combination on the William Herschel
Telescope. Our dataset consists of 186 member stars, 159 of which have good
quality velocities, extending to a magnitude V=19.5 with a mean velocity
precision of 2 km/s. We find statistically strong evidence of a rising velocity
dispersion consistent with a dark matter halo with gently rising rotation
curve. There is a <2 sigma signature of rotation about the long axis,
inconsistent with tidal disruption being the source of the rising dispersion.
By comparing our dataset with earlier velocities, we find that Draco probably
has a binary distribution and fraction comparable to those in the solar
neighbourhood. We apply a novel maximum likelihood algorithm and fit the
velocity data to a two parameter spherical model with an adjustable dark matter
content and velocity anisotropy. Draco is best fit by a weakly tangentially
anisotropic distribution of stellar orbits in a dark matter halo with a very
slowly rising rotation law. We are able to rule out both a mass-follows-light
distribution and an extended halo with a harmonic core at the 2.5 to 3 sigma
significance level, depending on the details of our assumptions about Draco's
stellar binary population. Our modelling lends support to the idea that the
dark matter in dwarf spheroidals is distributed in the form of massive, nearly
isothermal haloes.
