Liverpool can claim precedence for mercantile marine signalling, which differed from that used in the Royal Navy. By 1816, Liverpool employed a numerical system of flags (0, 1, 2 etc). Vessels regularly using the Mersey were allocated a three figure number which was to be hoisted when in sight of the signal station at Holyhead and Bidston. Once the vessel has “made its number” , its onward transmission to Liverpool was quite different depending on whether it was Holyhead or Bidston. In the case of Holyhead, the information was sent by post at 1pm and arrived at Liverpool early the next morning. However for Bidston, the lookout indicated the vessel’s owner using a flag or shape at a particular point on one of the scores of flagpoles arranged on the ridge of Bidston Hill. In most cases the owner would be expecting the notification as it would have received the early warning from Holyhead.
This process also allowed them to detect masquerading enemy vessels or privateers that frequented the Irish Sea as the lookouts knew what each Liverpool ship looked like, so usage of another ship’s numbers didn’t work.
Once peace was restored following the French Wars, Captain Marryat R.N. was one of the few to realise the necessity for individual vessels of the Merchant Navy to be able to communicate with each other and the shore. Other codes were produced but his won approval from the hierarchy.
For Liverpool, with hindsight, it would have been preferable to scrap the existing flags and adopt Marryat’s Code and flags. However the Liverpool/Holyhead flags and ships numbers was well established amongst the regular users of the Mersey and a change would have caused a storm of protest. The Liverpool Dock Board Trustees decided on a chain of signal stations between Holyhead and Liverpool and a more sophisticated two way form of communication and to eliminate the delay between Holyhead and Liverpool. In 1826 they appointed Barnard Lindsay Watson to be responsible for the design, construction and supervision of the whole system.
Watson published the “Code of Signals for the Merchant Service”, which built on the earlier system. What was new was the ‘code’ or dictionary of sentences, phrases and words covering most situations likely to arise between ship and shore.
For about 20 years Watson’s code persisted, until gradually superseded by Marryat’s.
Marryat’s codes were eventually superceded by the more globally useful Commercial Code (1857-1900).