I want to know the answer to the following question:
What prevented France's 819-line system from achieving the definition it was capable of?
All the background I'm provided with is that "The 240-line system could have doubled its frame rate but this would have meant that the transmitted signal would have doubled in bandwidth, an unacceptable option as the video baseband bandwidth was required to be not more than 3 MHz.". Is that enough to answer the question?
Answer: no