  We review some universal features of the colour flux tube of gauge theories
in the confining phase predicted by the infrared conformal limit of the
underlying string theory. In particular we discuss shape effects in Wilson
loops and rederive in a general way the logarithmic growth of the mean square
width of the flux tube as a function of the interquark separation. Recent data
on three-dimensional Z_2 gauge theory, combined with high precision data on the
interface physics of the 3D Ising model fit nicely to this behaviour over a
range of more than two orders of magnitude
