The best thing about making a television documentary is that you get to visit and gain access to locations you would either not be allowed to see or simply did not know about. In the past few years I have had the privilege of holding Newton’s first edition Principia Mathematica (and even checked out some of his sums – they were correct); I’ve stood on Galileo’s lecturing pulpit, looked through Herschel’s telescope and leafed through Michael Faraday’s notebook.

In fact, as I write and think back to the seven or eight science documentary series I have made over the past few years, many such memories come flooding back. Of course not all scientists get sentimental about such important artefacts from the history of science, but for me they bring the subject alive and fill me with a sense of pride that I am playing my small part in advancing scientific knowledge. These are the giants on whose shoulders I stand.

The most recent such occasion when I was filled with wonder was somewhat unexpected. I am currently filming a three-part series on the history of electricity. Last week I was with the BBC crew in Cornwall to tell the story of the laying of the first transatlantic telegraph cable in 1858. I knew nothing about this subject until recently and it turned out to be tremendously fascinating. The story I was telling was of the two ships that sailed out the mid-Atlantic, each carrying one thousand miles of cable an inch in diameter and weighing 1000 tons. No single ship could carry the whole length that would stretch the two thousand miles from the west coast of Ireland to New Foundland. In mid-Atlantic, the two halves were spliced together, dropped into the Ocean and the two ships headed apart to either coast, dropping the cable as they went.

That afternoon, the film crew and I moved from the chilly beach to the Porthcurno Telegraph Museum where I was filmed talking about how the very first message, sent by Queen Victoria to America, took 16 hours – due to the problem of what is called ‘retardation’ the Morse code had to be sent slowly and repeated over and over again in order to be deciphered and understood at the other end. You see two thousand miles of copper wire acts as a capacitor and stores up electric charge so sending a more code ‘dot’ as a sharp pulse gets stretched out into a slow rise and slow drop in voltage at the other end and they had trouble working out their dots from their dashes. The problem was resolved in an incredibly simple way: rather than dots and dashes, they would simply reverse the polarity of the electric circuit that was producing the pulse. So, the current goes round one way for a dot and the opposite way for a dash.

The final part of day was the highlight for me, for it was then that I was able to explain how the very weak electric signal was picked up at the receiving end. One of the most important characters in the story was also one of the 19th century’s most famous physicists: William Thompson (later Lord Kelvin). He invented a device called the mirror galvanometer that got to see a replica of and explain in satisfying detail. But I will leave it to you to look that up!