Lavernock () is a hamlet in the Vale of Glamorgan in Wales, lying on the coast south of Cardiff between Penarth and Sully, and overlooking the Bristol Channel. Marconi and the first radio messages across open sea Following overland tests at Salisbury Plain during March 1897, on 13 May 1897, the Italian born and recently British based inventor, best known for his development of a radiotelegraph system, Guglielmo Marconi, assisted by George Kemp (who was a Cardiff based Post Office engineer) transmitted and received the first wireless signals over open sea between Lavernock Point and Flat Holm island. The very first message transmitted in morse code was "ARE YOU READY". This was immediately followed by "CAN YOU HEAR ME" to which the reply was "YES LOUD AND CLEAR". The morse recording slip for the first message is on display in the National Museum of Wales. Following the initial opening exchange there followed detailed technical messages in both directions indicating each end's equipment settings and receiving sound levels. Marconi indicated that he was using a spark on his equipment. The successful test followed several days of trials and failure while adjustments were made to aerial length. Extensive trials were carried out over the remainder of the week in various weather conditions and with different settings on the equipment at each end. Marconi benefitted from the active encouragement of then Mr. William Preece (later Sir William Preece) who was Engineer-in-Chief of the Post Office and had himself transmitted radio telegraph morse signals across Coniston Water eight years earlier. Preece had been previously acted as a consultant to the Bristol Corporation's Electricity Department between 1883 and 1893. The Post Office engineers, including George Kemp who kept a detailed diary of these events, had been experimenting for some months at Lavernock Point. Kemp recorded the following in his diary of the experiments: "Mr Marconi's apparatus was set up on the cliff at Lavernock Point, which is about twenty yards above sea-level. Here we erected a pole, high, on the top of which was a cylindrical cap of zinc, long and diameter. Connected with this cap was an insulated copper wire leading to one side of the detector, the other side of which was connected to a wire led down the cliff and dipping into the sea. At Flat Holm Mr Preece's apparatus was arranged, the Ruhmkorff coil also giving sparks from an eight-cell battery.