  We demonstrate the existence of a secular back-reaction on inflation using a
simple scalar model. The model consists of a massless, minimally coupled scalar
with a quartic self-interaction which is a spectator to $\Lambda$-driven
inflation. To avoid problems with coincident propagators, and to make the
scalars interact more like gravitons, we impose a covariant normal ordering
prescription which has the effect of removing tadpole graphs. This version of
the theory exhibits a secular slowing at three loop order due to interactions
between virtual infrared scalars which are ripped apart by the inflating
background. The effect is quantified using an invariant observable and all
orders bounds are given. We also argue that, although stochastic effects can
have either sign, the slowing mechanism is superimposed upon them.
