The events centred on Marconi's factory in New Street, Chelmsford which had already been dabbling in broadcasting experiments from its test station at the plant with the call sign MZX (Marconi Zulu X-Ray). Just a year earlier the Marconi Company had successfully transmitted across the Atlantic from a site at Ballybunion in Ireland under the supervision of engineers H.J. Round and W.T. Ditcham. It was Ditcham who had the honour to be the first European voice to be heard over the airwaves on the other side of the Atlantic.
Back at Chelmsford in January 1920 Ditcham and Round had built a 6 kilowatt transmitter (increased to 15 kilowatts in February) using an aerial slung between two 450 feet masts for more experimental broadcasts. Though chiefly used for speech test transmissions another engineer, G.W. White also organised some musical interludes. For this they roped in staff from the factory, two assistants, W. Higny and A. Beeton, played the cornet and oboe, a research engineer played a one-string fiddle and White could be heard at the piano. Vocalists were Edward Cooper, who worked in the mounting shop, the possessor "of a tenor voice of more than average quality" and soprano Winifred Sayer who worked at the Hoffman Manufacturing Co. in the town. Ditcham himself was back at the microphone where he gave "a nightly recital of the railways of Great Britain and their London termini (which) gave much amusement to those who listened".
Onto the scene comes amateur radio enthusiast, and former wartime signals officer, Tom Clarke who just happened to work as an assistant to Lord Northcliffe, owner of the Daily Mail. The paper had already been reporting on some early wireless experiments and a receiving station was installed in their offices. Clarke had already established a good relationship with Arthur Borrows at Marconi so it's not clear who first came up with the idea of persuading Northcliffe that a public broadcast with a star name would help boost the fledgling media and provide some great publicity for the newspaper. That star name was the singing sensation of the age, Australian opera singer Dame Nellie Melba, who was back in the UK after the war and performing at the Royal Opera House in Covent Garden.
Melba was enticed up to Chelmsford with a £1,000 fee, though she was initially reluctant to indulge what she saw as wireless enthusiasts and their "magic playboxes". On 15 June 1920 she took the train up from London accompanied by her son, daughter-in-law and her two piano accompanists Frank St Ledger and Herman Bemberg. The planned broadcast wasn't without its some technical hitches. The studio set up in the main building had to be abandoned following a power surge and they decamped to the experimental shed, taking some rolled-up carpet to help the acoustics in the concrete floored workshop.
On being showed around the plant and looking up at the masts Melba is supposed to have said to Burrows: "Young man. I am Dame Melba. If you think for one moment that I'm going to climb up there I'm afraid you are very much mistaken."
In his The Story of Broadcasting Burrows described what happened next: " The few hundred experimenters who adjusted their receivers to 2,800 metres on the evening of June 15, 1920, heard promptly at 7.10 p.m. something infinitely more beautiful than a note of mechanical origin. It was a prolonged trill from the throat of one of the sweetest singers of the century. Five minutes later there rippled across the ether the stirring sounds of Home Sweet Home then Nymphes et Sylvains in French and Addio from La Boheme".
Although Burrows didn't relate this there was a break in the transmission and Dame Nellie was asked to return to the microphone where she continued with Chant Venitien, a reprise of Nymphes et Sylvains and ending with God Save the King.
The short broadcast was heard all over the country by those that had built their crystal sets, including a fair share of wireless operators and electrical engineers, and by those Wireless Clubs that were starting to spring up. "It was a wonderful half-hour" proclaimed the Daily Mail.
Those listening in mainland Europe also heard the broadcast. Burrows explains: "Next day there arrived from most European countries telegrams containing expressions of wonder and appreciation. At Christiania the signals were so strong that the operator at the wireless station some distance from the town relayed the music by telephone to the principal newspaper offices. In France a phonograph record was actually made in the operating room beneath the Eiffel Tower".
Marconi engineer Harry Dowsett was moved to write that the Melba broadcast was "a great initiation ceremony, and the era of broadcasting for the public amusement ... may be said to have completed its preliminary trails and to have been definitely launched on its meteoric career from this date".
More successful trails were run by Marconi engineers over the summer of 1920 but it all came to a grinding halt that November following complaints, mainly from the Armed Services, made to the Postmaster General that they were "interfering with important communications" (not dissimilar to the responses made about the offshore pirates four decades later). Others opined that these "stunts" were a "frivolous" use of a national service." Whilst the Post Office continued to grant amateur licences for transmitting sets of 10 watts or less it wasn't until February 1922 that radio broadcast experiments resumed from 2MT from Writtle. Three months later 2LO from Marconi House in London took to the air and a new chapter in British broadcasting started.
You can hear more about the 100th anniversary of this famous broadcast today on BBC Essex and Chelmsford Community Radio.
Listen out too for the fourth episode of Paul Kerensa's new podcast series The British Broadcasting Century.
Tim Wander's play The Wireless Sings is on YouTube.
David Lloyd has written a blog post about Nellie's First Drivetime Show.
Read about this and much more in Charlie Connelly's excellent Last Train to Hilversum.