Report on talk by Mark Thompson on Telegraphs on the Lines of Torres Vedras

Around 30 members and guests gathered at ALA, the Academia de Letras e Artes, in Monte Estoril on 18 October to hear this talk by Mark Thompson (below). As we learnt during the introduction given by Mark Crathorne, Dr. Thompson has published 15 books on the Peninsular War, most recently an excellent book entitled Wellington and the Lines of Torres Vedras, reviewed in our Newsletter 23.

In planning the Lines, Wellington realised that he may have had to move forces rapidly from one defensive position to another to counter the French threat. But how was he to get rapid advice on which points the French were threatening? Land-based signalling seemed to be a solution. Mark Thompson pointed out that such signalling was not new, going back thousands of years. Until 1809, when Wellington gave instructions for the Lines to be started, the most effective signalling system had been designed by Claude Chappe (below) during the French Revolution. This was a complex, fixed system that offered over 200 combinations and could relay messages from point to point very rapidly. Mark’s slides well illustrated how the system worked.

In Portugal, there had been a system in place for some time to advise Lisbon when ships were arriving, called the Ciera system (below). In 1810 the Corpo Telegráfico was founded and it implemented an easy-to-use system that connected Lisbon with Almeida, Abrantes and Elvas. There had also been signalling between Lisbon and Mafra Palace to keep the King informed of events, before the Royal Family relocated to Brazil as a result of the first French invasion.

The first mention of such a system on the Lines was on 1 April 1810, when Wellington noted that he had been talking to Admiral George Berkeley to enquire how the Royal Navy’s communication expertise could be employed. Based on the Navy’s methods, a system (below) was designed using balls and flags that could provide over 20,000 combinations, with nine or ten signalling stations. Officers would use a code book of phrases likely to be needed and these would be transmitted as a short string of numbers. It was agreed that sailors would be seconded to the Lines to provide the necessary operational expertise. At one time Berkeley withdrew them because they had not been paid agreed bonuses. Later he relented, perhaps not wishing to go down in posterity as the person who had caused the British defeat.

It emerged from Mark’s talk that there is much information missing about the Lines telegraph system. It is generally agreed, although not certain, that there were up to eleven stations (see map below). However, as they did not all have line of sight with each other and, in some cases were too far away, messages had to be sent from one station to another through a third. Exactly what system was employed to do this is unknown. Did messages go clockwise or anti-clockwise? It was a slow, complicated business to turn the station round to point it in the direction of a different station and the recipient station would have to be expecting the transmission. Thus, Mark speculated that a message would just be sent to the next station with instructions to forward it to the intended recipient. Construction of the telegraph stations did identify one serious problem, which was that British telescopes were inadequate. Steps were quickly taken to procure new ones.

In response to some very interesting questions and observations from the audience, particularly the Portuguese members present, Mark further indicated other areas in which information was far from complete. For instance, he stated that there was no indication that the system had ever been used in anger as there were no records of any communications having been made. As the French stumbled at the first hurdle this could indeed have been the case but a failure by officers to keep a record of messages sent or received seems a more likely explanation. Mark also confessed to not knowing the material used for the balls in the system.

With these topics for further research, the meeting concluded with a hearty vote of thanks for Mark Thompson and the hope that he could give further talks during future visits to Portugal.

For those seeking more information on the topic, see Chapter 8 of Wellington and the Lines of Torres Vedras, by Mark Thompson. Helion & Co. 2021. Isbn 978-1-914059-85-8

AWS