This paper contains a small improvement to the explicit bounds on the growth
of the function $S(T)$. It is shown how more substantial improvements are
possible if one has better explicit bounds on the growth of
$|\zeta(\frac{1}{2}+it)|$.
This paper refines the argument of Lehman by reducing the size of the
constants in Turing's method. This improvement is given in Theorem 1 and scope
for further improvements is also given. Analogous improvements to Dirichlet
L-functions and Dedekind zeta-functions are also included.