There was a young fellow of Italy
Who diddled the public quite prettily
Maskelyne was largely self-taught in wireless technology. He had figured out that Marconis claims of true "Hertzian Syntony" were bunk. Maskelyne simply overrode the transmission with an untuned transmitter using a 10 inch induction coil. He knew that Marconi had been specializing in long waves so he used a shorter frequency to bleed in from any resonant frequency. Knowing the lecture began at 5:00 PM, he began his trolling promptly at 5:45 PM. In a word... tango down. More here.
Maskelyne was a stage magician by trade and had learned Morse code to communicate with his hands during shows. He learned wireless gear well enough to make a spark-gap transmitter to remotely ignite gunpowder. In 1900, he sent wireless messages between a ground station and a balloon 10 miles away. His ire for Marconi began with his excessively broad patents. It impeded him and other inventors working in early wireless. So he set up a 50 meter antenna near Porthcurno to snoop on the Marconi ship-to-shore transmissions. More here.
It was important that day that Maskelyne proved that wireless transmissions were not secure in any sense of the word. Fleming tried to claim later that Maskelyne had somehow cheated by using an earth ground that his interference was not "fair." But the truth was that those early tuned systems were totally vulnerable to the even earlier untuned or "dirty" systems. Marconi had been trolled hard and lost. Fleming claimed that his instruments were configured in such a way that interference could not occur, but it did anyway. Editorials of the day gave some credit and praise to Maskelyn's legitimate criticism but others did not appreciate the crudity within their "sacred" institution. The book Scientific Credibility and Technical Standards by Jed Z Buchwald covers the event in great detail.
Maskelyn, Fleming and Marconi argued in the pages of a trade magazine called The Electrician for a couple weeks then in July, realizing that Maskelyne was indeed a troll, a troll of historic proportions. They ceased to respond to his further taunts and in the future they limited their public displays. In 1905 Fleming invented a more precise AC rectifier that was actually able to do what he'd claimed 3 years prior.