This essay discusses a previously-unknown copy of Andrew Marvell’s Mr Smirke, which features annotations in his hand. We argue that the recipient of the volume was the Anglo- Dutch agent ‘William Freeman’, who was closely involved with a Dutch fifth column, set up by William of Orange and his spymaster Pierre Du Moulin, which lobbied Parliament during the Third Anglo-Dutch War. The essay discusses further archival evidence of Marvell’s links to Freeman, and argues that their connection persisted after the end of the Third Anglo-Dutch war. Finally, the essay argues that these links throw new light onto the development of Marvell’s late prose work, An Account of the Growth of Popery and Arbitrary Government, which is more closely influenced by other pamphlets associated with William’s propaganda efforts in England in the 1670s than has been hitherto realised.