  The maximum labelled clique problem is a variant of the maximum clique
problem where edges in the graph are given labels, and we are not allowed to
use more than a certain number of distinct labels in a solution. We introduce a
new branch-and-bound algorithm for the problem, and explain how it may be
parallelised. We evaluate an implementation on a set of benchmark instances,
and show that it is consistently faster than previously published results,
sometimes by four or five orders of magnitude.
