Gravitational lensing of the cosmic microwave background (CMB) can obscure some signals, converting E-mode into B-mode polarisation and acting as a source of noise in the search for inflationary gravitational-wave signatures. Patricia Larsen of the Institute of Astronomy and the Kavli Institute for Cosmology in Cambridge and colleagues have now demonstrated delensing of Planck temperature maps using the cosmic infrared background. Using Planck maps at 545 and 857 GHz, the delensed CMB temperature anisotropies are measured at lower frequencies, with a sharpening of the acoustic peaks detected with a significance of 16 standard deviations. The technique is expected to be essential for further high-precision constraints on inflationary B-mode polarisation.