Although there has been considerable controversy over the years regarding who actually invented radio – controversy not helped by Marconi himself being at times over-willing to claim credit for the work of others – it is now generally agreed that it was Marconi himself who first invented radio. (The disputes mostly revolve around who invented various later refinements of Marconi’s original patent.)
That patent – British Patent 12039 “Improvements in Transmitting Electrical impulses and Signals, and in Apparatus therefor” – was applied for on June 2 of 1896, with the complete specification being provided on March 2 of the following year, and the patent as a whole being accepted on July 2, 1897.
Unfortunately for Marconi, Tesla had been granted similar patents in America, and the two men would spend decades locked acrimonious dispute over the matter. In fact, in America it would only be resolved by a court decision after both men had died – the court found in favour of Tesla. But perhaps Marconi won anyway – it’s his name, not Tesla’s, which is used as a synonym for ‘radio’ even today.