A team from the University of Cambridge has taken over a short, double track section of unused Post Office tunnel near Liverpool Street Station, where a newly built tunnel for Crossrail is situated some two metres beneath. The study is to establish how the original cast-iron lining sections, which are similar to those used for many miles of railway under London, resist possible deformation and soil movement caused by the new works. Digital cameras, fibre optic deformation sensors, laser scanners and other low-cost instruments, reporting in real time, have been installed in the vacated tunnel. As well as providing information about the behaviour of the old construction materials, the scheme can also provide an early warning if the new tunnel bores are creating dangerous soil movement.