Should the title not read, "BBC marks centenary of its first radio broadcast"?
Other entities had been broadcasting for many years before the BBC's services began.
Other entities had been broadcasting for many years before the BBC's services began.
See the current (2022-11-15) Features and Analysis sub-section at
https://www.bbc.com/news/entertainment_and_arts
Being as the article is on the BBC I suppose they expect the context to be understood :)
I've changed the submission title to the article title "Mystery of BBC radio's first broadcasts revealed 100 years on".