Firstly, I wanted to mention that the Cathedral is beautiful and it proved to be an excellent setting for the concert and the Bohemian Symphony Orchestra Prague were absolutely fantastic. The music was impeccable and the environment made the occasion even more special.
Unfortunately, the evening was somewhat of a disappointment by people on their phones both texting/on the internet, taking photos and in one instance, a phone ringing during a song which made it extremely difficult to enjoy.
I understand that there is a sign on the door as we walk in, which says no cameras or phones, however I believe this was of little use. The woman next to me was on her phone throughout the concert and I counted six other people in front of me filming at one time or another. My advice would be to perhaps have more than one sign for people to see, in case they miss the first one. They could also ask the person who checks tickets to mention to people as they come in or even spend two minutes at the beginning of the performance to make an announcement and kindly ask people to refrain from spoiling the concert for other people.
It might seem a little extreme, but also having a small locker area for people to physically leave their phones would be the most effective solution but I appreciate that this may not be realistic.
Overall, the event itself was fantastic but they need to be more strict with their rules.