  An extremely sensitive all-sky survey will be carried out in the
millimetre/submillimetre waveband by the forthcoming ESA mission Planck
Surveyor. The main scientific goal of the mission is to make very accurate
measurements of the spatial power spectrum of primordial anisotropies in the
cosmic microwave background radiation; however, hundreds of thousands of
distant dusty galaxies and quasars will also be detected. These sources are
much more likely to be gravitationally lensed by intervening galaxies as
compared with sources discovered in surveys in other wavebands. Here the number
of lenses expected in the survey is estimated, and techniques for
discriminating between lensed and unlensed sources are discussed. A practical
strategy for this discrimination is presented, based on exploiting the
remarkable sensitivity and resolving power of large ground-based
millimetre/submillimetre-wave interferometer arrays. More than a thousand
gravitational lenses could be detected: a sample that would be an extremely
valuable resource in observational cosmology.
