Post Keynesian economics has largely forgotten Steindl's insight that monopolisation of the corporate sector redistributes profits to those firms least likely to invest them productively. Agent-based methods can be used to incorporate Steindl's insights into a simple stock- flow consistent model of the monetary circuit. This model illustrates the `maldistribution of profits' and `enforced indebtedness' of heterogeneous firms alongside the tendency towards stagnation that occurs with rising monopolisation. The model also demonstrates Minsky's assertion that firms' leverage rises over the business cycle can be reconciled with Kalecki's macroeconomic identities showing that profits are `financed' by the investment expenditures of firms.