  We develop a new algorithm for the quantisation of systems with first-class
constraints. Our approach lies within the (History Projection Operator)
continuous-time histories quantisation programme. In particular, the
Hamiltonian treatment (either classical or quantum) of parameterised systems is
characterised by the loss of the notion of time in the space of true degrees of
freedom (i.e. the `problem of time'). The novel temporal structure of the HPO
theory (two laws of time transformation that distinguish between the temporal
logical structure and the dynamics) persists after the imposition of the
constraints, hence the problem of time does not arise. We expound the algorithm
for both the classical and quantum cases and apply it to simple models.
