A Boeing 720B passenger plane, D-ABOM, sustained substantial damage in a landing accident at London-Heathrow Airport (LHR). On final approach to London the crew discovered that the nose landing gear could not be lowered . After going round again the crew tried in vein by all means possible to lower the nose landing gear. A safe nosegear-up landing was carried out on runway 10L. PROBABLE CAUSES: “The investigation in London revealed a blockage, at the retracted position of the hydraulic system of the jack for retracting and lowering to nose landing gear; this was caused by foreign bodes (small pieces of rubber totalling about 6 cm2 in area) . The crew, therefore, had no possibility of lowering the landing gear.”