Mercury Communications Ltd is soon to begin a trial of an aerial fibre optic network system in conjunction with one of the Area Electricity Boards in the South of England, which if extended to other areas of the UK, could lead to rapid expansion of its network. Mercury will be testing two-mile fibre optic cable called Fibrespan, developed by STC Plc, which is designed to run over electricity pylons and co-exist without interference with existing power lines. If the trial, which is due to begin before the end of 1987, is successful it will be built into Mercury’s network. Mercury is looking into a number of ways of expanding its network in-cluding linking up with cable television operators such as Windsor Television and ELT in Docklands.