Poly(ether ether ketone) terminated with 4-phenoxyphenoxy end groups undergoes essentially quantitative condensation with a novel carboxy-functionalised macrocyclic ether-ketone in trifluoromethanesulfonic acid to afford a semi-crystalline, bis(macrocycle)-terminated polyketone, This new molecular architecture, characterised by NMR spectroscopy, DSC, MALDI-TOF mass spectrometry and - for a model oligomer - by single-crystal X-ray analysis, opens up new possibilities for in-situ chain extension and crosslinking of high-performance polymers.